Haven't been on the main matrix.org server for many years, but they used to have a lot of issues with latency - it wasn't really instant messaging but more like email. When I felt it was the worst, I decided on self hosting it. That improved things significantly - it started to behave like an instant msg platform. Now with OVH migration I am even able to scroll through hundreds of attachments super fast and everything feels snappy.

And I also know there is no online status on the main server. Other than that, no idea