I've been using the fedi-block-api for some time now. It's been a really helpful tool for me in determining which instances of federated platforms I want to make accounts on by making it easy to see what an instance blocks compared to who it is blocked by.
While the fedi-block-api is open source, I very much do not like the people behind it. Reasons being that the source code was initially hosted on KiwiFarms of all places, and the source code license containing a racial slur.
Fediseer. Its a chain of trust system where instance admins rate other instance admins
That way the block list isn't maintained by one person. You decide who you trust and you can follow who they trust and blcok all the instances censured by anyone along that chain