openHAB 4 migration FAQ

Dear community members, please respect forum policy / posting rules.
Stay on topic and stay tight. The topic is FAQ here.
For anything not strictly related and of relevance to the FAQ, open your own threads.
Same if you want to discuss any of the FA questions in more detail.
When you do in wide-ranged or overview-like threads like this one, it’s quickly becoming an unreadable mess.
Thank you.

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