Where do I set the community base URL?

Solid breakdown. The only thing I would add is to back up before making the change — better safe than sorry.

Tried this on a staging copy first and it behaved exactly as described. Confident enough to roll it to production now.

Appreciate the clear steps. The dry-run tip in particular saved me from a mistake I would not have caught otherwise.

Thanks for writing this up. Bookmarking it — the kind of thing I will want to reference again in a month.