If I have questions about general usage/ support of this website (startrek.website), what’s the correct community?

This one right here - Quark's.

If I am not sure of a rule for the website, where should I ask

Same as above, if it's a general question about rules and not an appeal of a specific mod action.

If I am not sure of a rule for a specific community, where should I ask?

We're still deciding on the best solution to contact an entire mod team, but for now, reaching out to a community moderator directly is probably the way to go.

Where should I ask to find a community on a specific topic?

Quark's would be the place for this, as well.

Related to 1, where should I have put this post?

Right where you put it was the right call!

Also, what about questions about Lemmy?

taps the "Quark's" sign