TBH you’re going to have to work against the network effect. The benefit of Facebook is that most people are on there, and you probably won’t be able to recreate a network with the same reach on any alternative — the privacy benefits of not being on Facebook are vast, though.

I would advise you not to pick a single new platform or service to replace fb but consider something like ActivityPub as a wider network that can connect your different profiles on the Fediverse — see https://fediverse.party/ for examples. You’re already on Lemmy, so there’s a start.

Others have already suggested Friendica and Hubzilla as fb alternatives. I’ve used the former in the past when the Fediverse was still not as developed as it is now, and I think with the user growth it will be a fair substitute for Facebook. The big benefit, as I said above, is that both Friendica and Hubzilla are ActivityPub capable, so you should be able to follow users and profiles on Lemmy, Mastodon, Writely and Pixelfed alike.