Shouldn't be yet - for facebook (I'm not fucking calling them meta) to track you across the internet on websites you don't use, they use a tracking pixel - a 1 pixel image that is included on the webpage which is loaded from facebook.com. To load this image your web browser sends facebook.com the cookies it always sends to facebook.com - i.e. your login information, and that's how facebook knows that it's you on that random-ass website that has nothing to do with facebook.

But note - you have to have cookies on facebook.com for this to work. So long as you never visit lemmy.facebook.com or whatever tf their federated instance is, they won't be able to track you since they can't associate you with your login via the tracking pixel - If I go to another lemmy instance, that lemmy instance has no idea that I'm actually @theblueredditrefugee@lemmy.dbzer0.com.

Well, this is based on my knowledge of how facebook tracking works. Maybe it's changed since I worked there.

Edit: Should note that, obviously, everything you post on lemmy is public, keeping a log of everything a user posts should be pretty easy, like what they did with revddit and such before the apipockalypse.