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.

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.