PowerShell function to create md5crypt string.

Get-Md5Crypt.ps1

function Get-Md5Crypt {
    <#
    .DESCRIPTION
        Generate a md5crypt string ($1$salt$hash)
    .PARAMETER String
        The string to hash
    .PARAMETER Salt
        The salt to use (can be a crypt string)
    .PARAMETER SaltSize
        In case no salt is provided generate one with length SaltSize (default: 10)
    .NOTES
        Thanks to Aaron Toponce explanation: https://pthree.org/2015/08/07/md5crypt-explained/
    #>
    param (
        [Parameter(Position=0,ValueFromPipeline)]
        [string]
        $String,

        [string]
        $Salt,

        [ValidateRange(3,100)]
        [int]
        $SaltSize = 10
    )

    if($String.Length -eq 0) {
        $pass = [System.Net.NetworkCredential]::new("", (Read-Host -AsSecureString -Prompt "Enter Password")).Password
        $repeat = [System.Net.NetworkCredential]::new("", (Read-Host -AsSecureString -Prompt "Repeat Password")).Password
        if(-not $pass.Equals($repeat)) {
            throw "Passwords didn't match!"
        }
        $String = $pass
    }

    if($Salt.Length -eq 0) {
        $Salt = (-join ((48..57) +(65..90) + (97..122) | Get-Random -Count $SaltSize | ForEach-Object {[char]$_}))
    }elseif($Salt.StartsWith('$1$')) {
        $Salt = ($Salt -split '\$')[2]
    }

    $md5 = new-object -TypeName System.Security.Cryptography.MD5CryptoServiceProvider
    $utf8 = new-object -TypeName System.Text.UTF8Encoding

    $pw = [byte[]]$utf8.GetBytes($String)
    $magic = [byte[]]$utf8.GetBytes('$1$')
    $bsalt = $utf8.GetBytes($Salt)

    $itoa64 = "./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"

    $tmp = [System.Collections.ArrayList]@()
    $tmp.AddRange($pw)
    $tmp.AddRange($bsalt)
    $tmp.AddRange($pw)
    $db = $md5.ComputeHash([byte[]]$tmp)

    $da_bytes = [System.Collections.ArrayList]@()
    $da_bytes.AddRange($pw)
    $da_bytes.AddRange($magic)
    $da_bytes.AddRange($bsalt)
    $i = $pw.Length
    while($i -gt 0) {
        if($i -gt 16) {
            $da_bytes.AddRange($db)
        }else{
            $da_bytes.AddRange($db[0..$($i-1)])
        }
        $i -= 16
    }

    $i = $pw.Length
    while($i -gt 0) {
        if($i -band 1) {
            $da_bytes.Add([byte]0) | Out-Null
        }else{
            $da_bytes.Add($pw[0]) | Out-Null
        }
        $i = $i -shr 1
    }

    $dc = [byte[]]$md5.ComputeHash([byte[]]$da_bytes)

    for($i = 0; $i -lt 1000; $i++) {
        $tmp = [System.Collections.ArrayList]@()
        if($i -band 1) {
            $tmp.AddRange($pw)
        }else{
            $tmp.AddRange($dc)
        }
        if($i%3) { $tmp.AddRange($bsalt) }
        if($i%7) { $tmp.AddRange($pw) }
        if($i -band 1) {
            $tmp.AddRange($dc)
        }else{
            $tmp.AddRange($pw)
        }
        $dc = [byte[]]$md5.ComputeHash([byte[]]$tmp)
    }

    $final = ''
    @(@(0,6,12),@(1,7,13),@(2,8,14),@(3,9,15),@(4,10,5)) | ForEach-Object {
        $x, $y, $z = $_
        $v = ([int]$dc[$x] -shl 16) -bor ([int]$dc[$y] -shl 8) -bor [int]$dc[$z]
        1..4 | ForEach-Object {
            $final += $itoa64[ $v -band 0x3f ]
            $v = $v -shr 6
        }
    }
    $v = [int]$dc[11]
    1..2 | ForEach-Object {
        $final += $itoa64[$v -band 0x3f]
        $v = $v -shr 6
    }

    '{0}{1}${2}' -f $utf8.GetString($magic),$salt,$final
}

Great!

To work with an UNIX appliance salt is max 8