Dropsitenews published a list of websites Facebook uses to train its AI on. Multiple Lemmy instances are on the list as noticed by user BlueAEther
Hexbear is on there too. Also Facebook is very interested in people uploading their massive dongs to lemmynsfw.
Full article here.
Link to the full leaked list download: Meta leaked list pdf
Oh yea absolutely. The point of going elsewhere is not for more privacy. The point is to make the content here neutral and in a sense unsellable. Nobody can buy your data on the fediverse, cause it's just there, freely given. Anyone can access it, so nobody can sell it.