i'm going to be scraping the bottom of the barrel here, so bear with me:

• cerulean - an experiment to do with threading features, so it is not guaranteed to be as good as lemmy, nor is it maintained
• commune - it feels more like discord, and has its own api in front of matrix, but it is still built on matrix!

yeah i dunno, there are others like somix and morum but they seem more early stages.