The migration app of choice appears to be .. xiaohongshu, or "little red book". I'm guessing this won't last since it wasn't intended to have lots of Westerners using it and neither government is going to be happy with that scale of unfiltered contact between ordinary Chinese citizens and US citizens. In the meantime, it's the place for Luigi Mangione memes.
Not that it makes a lot of difference to me, facebook is the only social-media-y thing I use and that is just under sufferance (only way to easily keep tabs on what is happening with some people, mainly family) and because I sometimes like to “breakfast with Lord Percy”. I might try bluesky at some pint as many contacts are moving from fb to there (though that seems rather twitter-like and that has never appealed to me even before I even knew Musk existed).