Fediblock

The Fediseer is primarily focused on anti-spam but it provides the censures functionality which you can use to mark which instances you don't want to associate with. You can then use the python SDK to automatically convert them into a blocklist. You can in fact combine your with the blocklists of other instances you trust, so as to crowdsource the maintenance of your blocklists.

You can also easily see which censures any instance has given, even if they're not in their blocklist with a simple URL. Example lemmy.dbzer0.com

We also have a Lemmy Community