You yourself say in a different comment that you are currently assessing Element:
https://news.ycombinator.com/item?id=34779070. Either you have a formed opinion Matrix, or you don't. Which one is it?
You keep saying Element instead of Matrix, and obviating the whole Matrix ecosystem. Matrix protocol has several server implementations, and many more things around:
https://matrix.org/docs/projects/try-matrix-now
To me it looks like they come with proprietary stuff: https://element.io/pricing
Especially Group Sync seems like something to drive you into their paid offerings, I assume by keeping the code close to the vest.