As much as I love (and still support) Matrix - this is the problem that Signal warned about with allowing multiple clients onto your platform. Not all of them support the same features and hold back the progress as you find incompatibilities with people you’re attempting to communicate with. Even Fluffy chat (at least last I tried it) was missing a bunch of features that forced me to go back to Element.

I’m not saying Matrix or Signal is better, just that there is a valid reason for Signal wanting people to use the “official” client, it ensures feature compatibility.