From what I've seen, communities don't migrate; they fragment. It's very hard to get a group to move, even if the new option is clearly better in the ways that matter to the group.
When I left Stack Exchange I joined the Codidact project, which is FLOSS and run by a non-profit foundation (disclosure: I'm on the board). We still have lots of things we want to improve (we're a very small team), but probably our biggest challenge is adoption -- attracting enough people who want to do Q&A and related knowledge-sharing somewhere that puts communities and people first and isn't driven by revenue goals. We've got communities for software development, Linux, and others, and I'd love to see them grow.
When I left Stack Exchange I joined the Codidact project, which is FLOSS and run by a non-profit foundation (disclosure: I'm on the board). We still have lots of things we want to improve (we're a very small team), but probably our biggest challenge is adoption -- attracting enough people who want to do Q&A and related knowledge-sharing somewhere that puts communities and people first and isn't driven by revenue goals. We've got communities for software development, Linux, and others, and I'd love to see them grow.