Hi, @Peter Koller Thanks for posting your question in the Microsoft Q&A forum.
I understand that you are trying in Postgres 16 version. are you dropping or creating the extensions? the error message you got is dropping so I am confused? you have to remove dependencies before dropping extensions. and if you want to add I hope you have added extensions under server parameter if not please check below steps.
I tried to add on my second database and was successfully added.
Regards
Geetha