I also made this comment before I realised what the OP was trying to achieve. I thought he was downvoted because he asked “stupid” question as I was barely awake at this point. Haha
I still think some communities would benefit from disabling them though. But as you say there probably isn’t a way to achieve that with current lemmy.
I don’t think it’s possible to migrate instance/community to a new domain yet. This is the reason why fmhy instance died after .ml domain got nuked and I haven’t heard of such feature so far.