What specific version/feature fragmentation and clients are you referring to? As is common now, newer Synapse drops support for older Postgres (for example). Voice and video calls is the only feature that I can think of that is half-assed in Element/ElementX or not implemented in some clients.

Otherwise, Element, Element X, FluffyChat, Fractal, freaking Cinny on Ubuntu Touch (!), and terminal-based gomuks all support basic functionality, DMs, rooms, encryption, and attachments.