I just opened Element X, tried to decline some spammy invite - "sorry, unknown error occured". Tried opening backup section in settings - "sorry, unknown error occured".
what server is this on? (as these sound like serverside issues). please can you submit debug logs so we can take a look? needless to say, this shouldn't be happening.
I join from the official matrix.org server.
It also federates to Gnome server and maybe some others, but they never synced properly so I never used it.
I don't think it is ready for prime time.