We have an application in PB2017R3 that we are running quite happily on Windows 11, naturally we had to test the application fully before we agree for this to be used. But in general I do not foresee a problem, even though Appeon say it's not supported. All that means is that they have not and will not test and support that environment.
Windows Server 2022 is a different question, but again I would expect the application would probaly work fine, but you have to test it first.
Having, said that the migration to PB2022R3 is not that bad. Except for the loss of SOAP and some windows sizing issues it was relativly simple. I would suggest that the PB upgrade is on your roadmap sooner rather than later. There will be other benefits to the upgrade.