I've tried a few times. It always felt... clunky?

I tried Element. UI felt slow, I was unable to find notifications in scrollback. Clicking the notification button would take me to random messages.

There are very many clients lighter than Element.

I just checked https://matrix.org/ecosystem/clients/

I'll try FluffyChat, thanks!

I tried it. It looks nice, but audio/video calls didn't work at all between two FluffyChat clients.

I remembered another issue with Matrix.

Signal and XMPP (via Quickly) have a simple phone number based signup workflow that my family have grown used to.

My family are not happy on having to remember/use passwords/keys. That's a shame, but is ultimately a constraint I have to deal with when persuading them to install/use an IM app.

Replying to myself... looks like some Matrix homeservers support OpenID-style login. That's probably fine for family.