This gist shows how to use variables defined in one deployment job in another with the runOnce strategy.

multi-job-variable-azure-pipeline.yml

name: TEST-$(Date:yyyyMMdd)-$(Build.BuildId)

trigger: none

parameters:
- name: env
  type: string
  default: 'test'

variables:
- name: vmImage
  value: 'ubuntu-latest'
  readonly: true

stages:
- stage: StageA
  jobs:
  - deployment: JobA
    environment: $(env)
    pool:
      vmImage: ${{variables.vmImage}}
    strategy:
      runOnce:
        deploy:
          steps:
          - task: PowerShell@2
            name: outputPowershell
            displayName: 'Generate variables'
            inputs:
              targetType: inline
              pwsh: true
              script: |
                Write-Host "##vso[task.setvariable variable=varA;isOutput=true]valueA"
                Write-Host "##vso[task.setvariable variable=varB;isOutput=true]valueB"
  - deployment: JobB
    environment: $(env)
    dependsOn: JobA
    pool:
      vmImage: ${{variables.vmImage}}
    variables:
      varA: $[ dependencies.JobA.outputs['JobA.outputPowershell.varA'] ]
      varB: $[ dependencies.JobA.outputs['JobA.outputPowershell.varB'] ]
    strategy:
      runOnce:
        deploy:
          steps:
          - task: PowerShell@2
            displayName: 'Dump variables'
            inputs:
              targetType: inline
              pwsh: true
              script: |
                Write-Host "varA:                  $(varA)"
                Write-Host "varB:                  $(varB)"