Upfront: mind the forum rules, no cross-posting.
I moved this discussion back here where it belongs.
Not at all.
Ubuntu is not supported nor it ever was.
Seems you never have been running Ubuntu. But it was you to claim that not me.
Plus, you misunderstand the term “supported”.
The fact that some system works or seems to is not the same as that it’s supported which means that vendors or in this case maintainers state that it should work, that they have verified it to work at least to some proper extent and that (at least in principle) they are willing to help i.e. support users when those have problems running it. Not supported does not mean it does not work. It means they’re not willing to help you with that.
Nope, this is part of what you still don’t understand:
apt is NOT a “perfect legitimate system command” to use on openHABian for the purpose of upgrading the system.
Read this part of the docs again (you should have before use).
And no, your statement shows you have not understood the relation and difference of openHABian and openHAB.