There's this exteremely useful table: https://gultsch.de/compliance_ranked.html
I had good experience with elaon.de, dismail.de and wiuwiu.de. Currently using the third.

I don't really know what the last column is about. :P OMEMO works just fine on wiuwiu.de <-> dismail.de or wiuwiu.de <-> neko.im (a couple of my friends use it)