It'important to notice that I first, on your advise, applied the program Qemu on my original machine.qcow2-file for repairing possible errors. Qemu reported repairing a lot of errors, and finally that this qcow2-file was now error-free (see nov 22).
I'll recap for you now the steps I took with the new Joomla 3.9.22-8 osx stack:
1. I installed and started the stack without removing the original .bitnami directory (+ subdirectories, containing amongst others the repaired qcow2-file) representing my original website that worked well under the former osx. This resulted in the error-message that the program couldn't find a required MAC-address.
2. Next I removed the original .bitnami directory and installed the new bitnami stack again, allowing it to install its own .bitnami directory containing the default Joomla website. This worked well. The default website appeared correctly.
3. Next I replaced, on your instruction, the machine.qcow2-file representing the default Joomla-website with the repaired machine.qcow-file representing my website.
I hope this is enough information for reproducing the error.