A growing number of instances (mainly of Mastodon so far) are signing an ‘Anti-Meta Fedi Pact’, pledging to block any instance owned by Meta in the fediverse.
I don’t know how big this will get or how effective it will be, but if you run a fediverse instance, you should take a look at this https://fedipact.online/
There are some large and mid-sized instances in the list. The big ones haven’t really signed up so far. My bet is that most of them are waiting to see how Meta’s platform will actually turn out.