https://codeberg.org/oliphant/blocklists/src/branch/main/blocklists. Feel free to pick a tier depending on the community you’re building. Tier0 is basically “the bare minimum” but you may want the others depending on the community you’re building up.

Note that this does not seem to include any Lemmy instances yet.

IIRC Lemmy doesn’t have a way of importing blocklists directly, so you’ll either have to whip up a quick script to do so or manually add things by hand, which is tedious and you will give up.