How to access "deploymentOutputs" from AzureResourceManagerTemplateDeployment (@3) task from Azure DevOps YAML pipeline?

I am developing YAML pipeline which is simply deploying a HUB resource based on a main.bicep file (there's ONLY azure ADF deploy through it for now) saved in my Azure DevOps repo. However, I need to have access to "output" of the deployment of the bicep - I need for instance the IDs of some of the Azure Resources which get deployed. (also the deployment works without issues >> at the END I do have the ADF deployed)

Here is the code: stages:

#  DEPLOYING INFRASTRUCTURE - HUB
  - stage: DeployHub
    displayName: Deploy Hub Infrastructure
    jobs:
      - deployment: DeployHub
        displayName: Deploy Hub Infrastructure
        environment: '$(testEnvironment)' #used for the manual approval conditions
        strategy:
         runOnce:
          deploy:
            steps:
            # the checkout will enable the use of "git diff" as to see which files have been modified in the latest commit at some point
            - checkout: git://${{ variables.my_org }}/my_project@refs/heads/feature_branch_01

          # Actual deployment of the resources - HUB
            - task: AzureResourceManagerTemplateDeployment@3
              name: ARM_Template_Deployment_HUB
              displayName: 'Bicep Deployment Task HUB'
              inputs:
                deploymentScope: 'Resource Group'
                azureResourceManagerConnection: '$(serviceConnection)'
                action: 'Create Or Update Resource Group'
                resourceGroupName: '$(rgTesting)'
                location: 'some_location'
                templateLocation: 'Linked artifact'
                csmFile: '$(Build.SourcesDirectory)/$(bicepFilePathHUB_Test)'
                deploymentMode: Incremental
                deploymentOutputs: 'armOutputsHUB'

So the question is:

1. How to access the armOutputsHUB?
2. Does it matter if I access it within the same JOB, Stage?
3. Where is it saved? - I read that all deployment type of jobs are saved in: "Deployment jobs use the $(Pipeline.Workspace) system variable." Source: https://learn.microsoft.com/en-us/azure/devops/pipelines/process/deployment-jobs?view=azure-devops However, I still couldn't find variable called 'armOutputsHUB'

What I have tried and it did NOT work:

1. Within the same job as next task:

            - task: PowerShell@2
              displayName: 'Parse ARM deploymentOutputs'
              env:
                ARM_OUTPUTS: $(armOutputsHUB)
              inputs:
                targetType: 'inline'
                errorActionPreference: continue
                workingDirectory: '$(Pipeline.Workspace)' #default is "$(Build.SourcesDirectory)"
                pwsh: true
                script: |
                  Write-Host "armOutputsHUB = $armOutputsHUB" # >>nothing inside
                  Write-Host "armOutputsHUB = $($armOutputsHUB)" # >> nothing inside
                  Write-Host "armOutputsHUB = $($ARM_Template_Deployment_HUB.armOutputsHUB)" # >> nothing inside

                  $outputsObject = $env:ARM_OUTPUTS | ConvertFrom-Json
                  # error: Conversion from JSON failed with error: Unexpected character encountered while parsing value: $. Path '', line 0, position 0.
                  Write-Host "outputsObject = $($outputsObject)"  # >>nothing inside
                  Write-Host "outputsObject = $outputsObject"  # >>nothing insi

Any ideas or solutions / code for me to test will be greatly appreciated!!

I've found a nice sample pipeline on GitHub for you. It's quite similar to some of your examples but the use of string quotes might be what you're missing.

The pipeline

- task: PowerShell@2
    name: 'SetDeploymentOutputVariables'
    displayName: 'Set Deployment Output Variables'
    inputs:
      targetType: inline
      script: |
        $armOutputObj = '$(deploymentOutputs)' | ConvertFrom-Json
        $armOutputObj.PSObject.Properties | ForEach-Object {
          $keyname = $_.Name
          $value = $_.Value.value

          # Creates a standard pipeline variable
          Write-Output "##vso[task.setvariable variable=$keyName;issecret=true]$value"

          # Display keys in pipeline
          Write-Output "output variable: $keyName"
        }
      pwsh: true