[Ubuntu] Insalled tools not in PATH in AzureDevOps VirtualMachineScaleSet

[RomanSchneiderSonova]

Hi all,
I am trying to set up an Azure VirtualMachineScaleSet in AzureDevOpsPipelines using the Ubuntu image created from your repository.
So far I managed to generate the image but when I try to use it in a scale set in DevOps I don't have the tools installed in the $PATH.

I am not sure what I am missing and don't really know where and when I would need to run the post generation scripts in my case.
Is there a beginner friendly documentation on the steps needed after the generation of the image?
Do I need to create the VM after creating the image, run the post gen scripts and regeneralize the image again? (tried that with no success)
Do I need to run the post gen scripts whenever the instance gets created in the VMscaleset? If yes, how? (tried to add a custom script extension in the scale set)
Any hints would be very much appreciated as I am somehow stuck for quite some time now.