https://support.microsoft.com/en-us/help/2999226/update-for-universal-c-runtime-in-windows

wix-bootstrap-download-ucrt-sample.wxs

<?xml version="1.0" encoding="utf-8"?>
<Wix xmlns="http://schemas.microsoft.com/wix/2006/wi"
  xmlns:bal="http://schemas.microsoft.com/wix/BalExtension"
  xmlns:util="http://schemas.microsoft.com/wix/UtilExtension">

  <Bundle
    Name="Example Product"
    Version="1.2.3.4"
    Manufacturer="John Doe"
    Copyright="© 2021 John Doe"
    AboutUrl="https://example.com/"
    UpgradeCode="01234567-89AB-CDEF-0123-456789ABCDEF"
    Condition="VersionNT >= v6.0">

    <BootstrapperApplicationRef
      Id="WixStandardBootstrapperApplication.RtfLicense">
      <bal:WixStandardBootstrapperApplication
        LicenseFile="license.rtf"
        ShowVersion="yes"
        SuppressOptionsUI="yes" />
    </BootstrapperApplicationRef>

    <!-- v6.0 Service Pack 2 -->
    <bal:Condition Message="This application requires Service Pack 2 for Windows Vista / Server 2008.">
      <![CDATA[NOT ((VersionNT = v6.0) AND (ServicePackLevel < 2))]]>
    </bal:Condition>

    <!-- v6.1 Service Pack 1 -->
    <bal:Condition Message="This application requires Service Pack 1 for Windows 7 / Server 2008 R2.">
      <![CDATA[NOT ((VersionNT = v6.1) AND (ServicePackLevel < 1))]]>
    </bal:Condition>

    <!-- v6.3 KB2919355 -->
    <util:FileSearch
      Id="HAL.DLL"
      Path="[WindowsFolder]System32\hal.dll"
      Result="version"
      Variable="NT603HALVER"
      Condition="VersionNT = v6.3" />
    <bal:Condition Message="This application requires S14 Update (KB2919355) for Windows 8.1 / Server 2012 R2.">
      <![CDATA[NOT ((VersionNT = v6.3) AND (NT603HALVER < v6.3.9600.17031))]]>
    </bal:Condition>

    <!-- ucrtbase.dll version -->
    <util:FileSearch
      Id="UCRTBASE.DLL"
      Path="[WindowsFolder]System32\ucrtbase.dll"
      Result="version"
      Variable="UCRTBASEVER" />
    <!-- universal crt version -->
    <Variable
      Name="UCRTVER"
      Type="version"
      Value="10.0.10240.0" />

    <Chain>

      <!-- use heat command to get RemotePayload attributes -->
      <!-- example: heat payload Windows6.0-KB2999226-x86.msu -o 60x86.wxs -->

      <!-- Windows Vista (x86) -->
      <MsuPackage
        Name="Windows6.0-KB2999226-x86-6.0.1.6.msu"
        DisplayName="Universal CRT"
        KB="KB2999226"
        Cache="no"
        Compressed="no"
        Permanent="yes"
        InstallCondition="(VersionNT = v6.0) AND NOT (VersionNT64) AND (NTProductType = 1)"
        DetectCondition="(VersionNT = v6.0) AND NOT (VersionNT64) AND (NTProductType = 1) AND (UCRTBASEVER >= UCRTVER)"
        DownloadUrl="https://download.microsoft.com/download/D/8/3/D838D576-232C-4C17-A402-75913F27113B/Windows6.0-KB2999226-x86.msu" >
        <RemotePayload
          ProductName="Package_for_KB2999226"
          Version="6.0.1.6"
          Description="http://support.microsoft.com?kbid=2999226"
          CertificatePublicKey="52868DFCA6E3AF2632389E6C1EE7D0468D3797D0"
          CertificateThumbprint="3BDA323E552DB1FDE5F4FBEE75D6D5B2B187EEDC"
          Hash="38A521378445B34BD222FA354D2D5059707285A6"
          Size="681351" />
      </MsuPackage>

      <!-- Windows Vista (x64) -->
      <MsuPackage
        Name="Windows6.0-KB2999226-x64-6.0.1.6.msu"
        DisplayName="Universal CRT"
        KB="KB2999226"
        Cache="no"
        Compressed="no"
        Permanent="yes"
        InstallCondition="(VersionNT = v6.0) AND (VersionNT64) AND (NTProductType = 1)"
        DetectCondition="(VersionNT = v6.0) AND (VersionNT64) AND (NTProductType = 1) AND (UCRTBASEVER >= UCRTVER)"
        DownloadUrl="https://download.microsoft.com/download/5/4/E/54E27BE2-CFB2-4FC9-AB03-C39302CA68A0/Windows6.0-KB2999226-x64.msu" >
        <RemotePayload
          ProductName="Package_for_KB2999226"
          Version="6.0.1.6"
          Description="http://support.microsoft.com?kbid=2999226"
          CertificatePublicKey="52868DFCA6E3AF2632389E6C1EE7D0468D3797D0"
          CertificateThumbprint="3BDA323E552DB1FDE5F4FBEE75D6D5B2B187EEDC"
          Hash="0BEFBB0B78588F7C9F17EAD1DA3ABEDA2B6F4C7F"
          Size="1131241" />
      </MsuPackage>

      <!-- Windows 7 (x86) -->
      <MsuPackage
        Name="Windows6.1-KB2999226-x86-6.1.1.7.msu"
        DisplayName="Universal CRT"
        KB="KB2999226"
        Cache="no"
        Compressed="no"
        Permanent="yes"
        InstallCondition="(VersionNT = v6.1) AND NOT (VersionNT64) AND (NTProductType = 1)"
        DetectCondition="(VersionNT = v6.1) AND NOT (VersionNT64) AND (NTProductType = 1) AND (UCRTBASEVER >= UCRTVER)"
        DownloadUrl="https://download.microsoft.com/download/4/F/E/4FE73868-5EDD-4B47-8B33-CE1BB7B2B16A/Windows6.1-KB2999226-x86.msu" >
        <RemotePayload
          ProductName="Package_for_KB2999226"
          Version="6.1.1.7"
          Description="http://support.microsoft.com?kbid=2999226"
          CertificatePublicKey="52868DFCA6E3AF2632389E6C1EE7D0468D3797D0"
          CertificateThumbprint="3BDA323E552DB1FDE5F4FBEE75D6D5B2B187EEDC"
          Hash="564F02E6419B9858949B0CD5A65E2C8C0944DD88"
          Size="629006" />
      </MsuPackage>

      <!-- Windows 7 (x64) -->
      <MsuPackage
        Name="Windows6.1-KB2999226-x64-6.1.1.7.msu"
        DisplayName="Universal CRT"
        KB="KB2999226"
        Cache="no"
        Compressed="no"
        Permanent="yes"
        InstallCondition="(VersionNT = v6.1) AND (VersionNT64) AND (NTProductType = 1)"
        DetectCondition="(VersionNT = v6.1) AND (VersionNT64) AND (NTProductType = 1) AND (UCRTBASEVER >= UCRTVER)"
        DownloadUrl="https://download.microsoft.com/download/1/1/5/11565A9A-EA09-4F0A-A57E-520D5D138140/Windows6.1-KB2999226-x64.msu" >
        <RemotePayload
          ProductName="Package_for_KB2999226"
          Version="6.1.1.7"
          Description="http://support.microsoft.com?kbid=2999226"
          CertificatePublicKey="52868DFCA6E3AF2632389E6C1EE7D0468D3797D0"
          CertificateThumbprint="3BDA323E552DB1FDE5F4FBEE75D6D5B2B187EEDC"
          Hash="54050A5F8AE7F0C56E553F0090146C17A1D2BF8D"
          Size="1034556" />
      </MsuPackage>

      <!-- Windows 8 (x86) -->
      <MsuPackage
        Name="Windows8-RT-KB2999226-x86-6.2.1.9.msu"
        DisplayName="Universal CRT"
        KB="KB2999226"
        Cache="no"
        Compressed="no"
        Permanent="yes"
        InstallCondition="(VersionNT = v6.2) AND NOT (VersionNT64) AND (NTProductType = 1)"
        DetectCondition="(VersionNT = v6.2) AND NOT (VersionNT64) AND (NTProductType = 1) AND (UCRTBASEVER >= UCRTVER)"
        DownloadUrl="https://download.microsoft.com/download/1/E/8/1E8AFE90-5217-464D-9292-7D0B95A56CE4/Windows8-RT-KB2999226-x86.msu" >
        <RemotePayload
          ProductName="Package_for_KB2999226"
          Version="6.2.1.9"
          Description="http://support.microsoft.com?kbid=2999226"
          CertificatePublicKey="52868DFCA6E3AF2632389E6C1EE7D0468D3797D0"
          CertificateThumbprint="3BDA323E552DB1FDE5F4FBEE75D6D5B2B187EEDC"
          Hash="2D93B4FF5C396FC6922BB7BAE2FFB12DCBF7B0A6"
          Size="625544" />
      </MsuPackage>

      <!-- Windows 8 (x64) -->
      <MsuPackage
        Name="Windows8-RT-KB2999226-x64-6.2.1.9.msu"
        DisplayName="Universal CRT"
        KB="KB2999226"
        Cache="no"
        Compressed="no"
        Permanent="yes"
        InstallCondition="(VersionNT = v6.2) AND (VersionNT64) AND (NTProductType = 1)"
        DetectCondition="(VersionNT = v6.2) AND (VersionNT64) AND (NTProductType = 1) AND (UCRTBASEVER >= UCRTVER)"
        DownloadUrl="https://download.microsoft.com/download/A/C/1/AC15393F-A6E6-469B-B222-C44B3BB6ECCC/Windows8-RT-KB2999226-x64.msu" >
        <RemotePayload
          ProductName="Package_for_KB2999226"
          Version="6.2.1.9"
          Description="http://support.microsoft.com?kbid=2999226"
          CertificatePublicKey="52868DFCA6E3AF2632389E6C1EE7D0468D3797D0"
          CertificateThumbprint="3BDA323E552DB1FDE5F4FBEE75D6D5B2B187EEDC"
          Hash="B5943B2700B56F5F8DC307A9E237F23FCA5D8B70"
          Size="1359820" />
      </MsuPackage>

      <!-- Windows 8.1 (x86) -->
      <MsuPackage
        Name="Windows8.1-KB2999226-x86-6.3.1.9.msu"
        DisplayName="Universal CRT"
        KB="KB2999226"
        Cache="no"
        Compressed="no"
        Permanent="yes"
        InstallCondition="(VersionNT = v6.3) AND NOT (VersionNT64) AND (NTProductType = 1)"
        DetectCondition="(VersionNT = v6.3) AND NOT (VersionNT64) AND (NTProductType = 1) AND (UCRTBASEVER >= UCRTVER)"
        DownloadUrl="https://download.microsoft.com/download/E/4/6/E4694323-8290-4A08-82DB-81F2EB9452C2/Windows8.1-KB2999226-x86.msu" >
        <RemotePayload
          ProductName="Package_for_KB2999226"
          Version="6.3.1.9"
          Description="http://support.microsoft.com?kbid=2999226"
          CertificatePublicKey="52868DFCA6E3AF2632389E6C1EE7D0468D3797D0"
          CertificateThumbprint="3BDA323E552DB1FDE5F4FBEE75D6D5B2B187EEDC"
          Hash="9B1962825FA58DB8AAB777C72AF58B21E0AA276E"
          Size="603348" />
      </MsuPackage>

      <!-- Windows 8.1 (x64) -->
      <MsuPackage
        Name="Windows8.1-KB2999226-x64-6.3.1.9.msu"
        DisplayName="Universal CRT"
        KB="KB2999226"
        Cache="no"
        Compressed="no"
        Permanent="yes"
        InstallCondition="(VersionNT = v6.3) AND (VersionNT64) AND (NTProductType = 1)"
        DetectCondition="(VersionNT = v6.3) AND (VersionNT64) AND (NTProductType = 1) AND (UCRTBASEVER >= UCRTVER)"
        DownloadUrl="https://download.microsoft.com/download/9/6/F/96FD0525-3DDF-423D-8845-5F92F4A6883E/Windows8.1-KB2999226-x64.msu" >
        <RemotePayload
          ProductName="Package_for_KB2999226"
          Version="6.3.1.9"
          Description="http://support.microsoft.com?kbid=2999226"
          CertificatePublicKey="52868DFCA6E3AF2632389E6C1EE7D0468D3797D0"
          CertificateThumbprint="3BDA323E552DB1FDE5F4FBEE75D6D5B2B187EEDC"
          Hash="3ACBF3890FC9C8A6F3D2155ECF106028E5F55164"
          Size="1005170" />
      </MsuPackage>
      
      <!-- Windows Server 2008 (x86) -->
      <MsuPackage
        Name="Windows6.0-KB2999226-x86-6.0.1.6-s.msu"
        DisplayName="Universal CRT"
        KB="KB2999226"
        Cache="no"
        Compressed="no"
        Permanent="yes"
        InstallCondition="(VersionNT = v6.0) AND NOT (VersionNT64) AND NOT (NTProductType = 1)"
        DetectCondition="(VersionNT = v6.0) AND NOT (VersionNT64) AND NOT (NTProductType = 1) AND (UCRTBASEVER >= UCRTVER)"
        DownloadUrl="https://download.microsoft.com/download/B/5/7/B5757251-DAB0-4E23-AA46-ABC233FDB90E/Windows6.0-KB2999226-x86.msu" >
        <RemotePayload
          ProductName="Package_for_KB2999226"
          Version="6.0.1.6"
          Description="http://support.microsoft.com?kbid=2999226"
          CertificatePublicKey="52868DFCA6E3AF2632389E6C1EE7D0468D3797D0"
          CertificateThumbprint="3BDA323E552DB1FDE5F4FBEE75D6D5B2B187EEDC"
          Hash="38A521378445B34BD222FA354D2D5059707285A6"
          Size="681351" />
      </MsuPackage>

      <!-- Windows Server 2008 (x64) -->
      <MsuPackage
        Name="Windows6.0-KB2999226-x64-6.0.1.6-s.msu"
        DisplayName="Universal CRT"
        KB="KB2999226"
        Cache="no"
        Compressed="no"
        Permanent="yes"
        InstallCondition="(VersionNT = v6.0) AND (VersionNT64) AND NOT (NTProductType = 1)"
        DetectCondition="(VersionNT = v6.0) AND (VersionNT64) AND NOT (NTProductType = 1) AND (UCRTBASEVER >= UCRTVER)"
        DownloadUrl="https://download.microsoft.com/download/A/7/A/A7A70B17-ADF9-4FC3-A722-69FA89B79756/Windows6.0-KB2999226-x64.msu" >
        <RemotePayload
          ProductName="Package_for_KB2999226"
          Version="6.0.1.6"
          Description="http://support.microsoft.com?kbid=2999226"
          CertificatePublicKey="52868DFCA6E3AF2632389E6C1EE7D0468D3797D0"
          CertificateThumbprint="3BDA323E552DB1FDE5F4FBEE75D6D5B2B187EEDC"
          Hash="0BEFBB0B78588F7C9F17EAD1DA3ABEDA2B6F4C7F"
          Size="1131241" />
      </MsuPackage>

      <!-- Windows Server 2008 R2 (x64) -->
      <MsuPackage
        Name="Windows6.1-KB2999226-x64-6.1.1.7-s.msu"
        DisplayName="Universal CRT"
        KB="KB2999226"
        Cache="no"
        Compressed="no"
        Permanent="yes"
        InstallCondition="(VersionNT = v6.1) AND (VersionNT64) AND NOT (NTProductType = 1)"
        DetectCondition="(VersionNT = v6.1) AND (VersionNT64) AND NOT (NTProductType = 1) AND (UCRTBASEVER >= UCRTVER)"
        DownloadUrl="https://download.microsoft.com/download/F/1/3/F13BEC9A-8FC6-4489-9D6A-F84BDC9496FE/Windows6.1-KB2999226-x64.msu" >
        <RemotePayload
          ProductName="Package_for_KB2999226"
          Version="6.1.1.7"
          Description="http://support.microsoft.com?kbid=2999226"
          CertificatePublicKey="52868DFCA6E3AF2632389E6C1EE7D0468D3797D0"
          CertificateThumbprint="3BDA323E552DB1FDE5F4FBEE75D6D5B2B187EEDC"
          Hash="54050A5F8AE7F0C56E553F0090146C17A1D2BF8D"
          Size="1034556" />
      </MsuPackage>

      <!-- Windows Server 2012 (x64) -->
      <MsuPackage
        Name="Windows8-RT-KB2999226-x64-6.2.1.9-s.msu"
        DisplayName="Universal CRT"
        KB="KB2999226"
        Cache="no"
        Compressed="no"
        Permanent="yes"
        InstallCondition="(VersionNT = v6.2) AND (VersionNT64) AND NOT (NTProductType = 1)"
        DetectCondition="(VersionNT = v6.2) AND (VersionNT64) AND NOT (NTProductType = 1) AND (UCRTBASEVER >= UCRTVER)"
        DownloadUrl="https://download.microsoft.com/download/9/3/E/93E0745A-EAE9-4B5A-B50C-012F2D3B6659/Windows8-RT-KB2999226-x64.msu" >
        <RemotePayload
          ProductName="Package_for_KB2999226"
          Version="6.2.1.9"
          Description="http://support.microsoft.com?kbid=2999226"
          CertificatePublicKey="52868DFCA6E3AF2632389E6C1EE7D0468D3797D0"
          CertificateThumbprint="3BDA323E552DB1FDE5F4FBEE75D6D5B2B187EEDC"
          Hash="B5943B2700B56F5F8DC307A9E237F23FCA5D8B70"
          Size="1359820" />
      </MsuPackage>

      <!-- Windows Server 2012 R2 (x64) -->
      <MsuPackage
        Name="Windows8.1-KB2999226-x64-6.3.1.9-s.msu"
        DisplayName="Universal CRT"
        KB="KB2999226"
        Cache="no"
        Compressed="no"
        Permanent="yes"
        InstallCondition="(VersionNT = v6.3) AND (VersionNT64) AND NOT (NTProductType = 1)"
        DetectCondition="(VersionNT = v6.3) AND (VersionNT64) AND NOT (NTProductType = 1) AND (UCRTBASEVER >= UCRTVER)"
        DownloadUrl="https://download.microsoft.com/download/D/1/3/D13E3150-3BB2-4B22-9D8A-47EE2D609FFF/Windows8.1-KB2999226-x64.msu" >
        <RemotePayload
          ProductName="Package_for_KB2999226"
          Version="6.3.1.9"
          Description="http://support.microsoft.com?kbid=2999226"
          CertificatePublicKey="52868DFCA6E3AF2632389E6C1EE7D0468D3797D0"
          CertificateThumbprint="3BDA323E552DB1FDE5F4FBEE75D6D5B2B187EEDC"
          Hash="3ACBF3890FC9C8A6F3D2155ECF106028E5F55164"
          Size="1005170" />
      </MsuPackage>

    </Chain>

  </Bundle>

</Wix>

Beautiful! Thank you!