The Matrix clients I have tried have "call via audio" and "call with video" buttons available in convenient places.

> fwiw if you use the Jitsi widget, you can share the URL to your Jitsi room with anyone and they do not need Element or Matrix to join.

I would like my grandma to click a green "phone" button and answer my call. I would like my grandma to be able to issue a call for me.

> and the participants then need to agree on some server/software combo that provides the actual video conferencing.

Since the button is in a very convenient place, I would expect the integration to be a bit deeper than "hope the client understands the invite"; it's tricky to make the clients without a spec.

It would have been nicer if this were documented better/more obviously, so we know what to expect if we want video calls to work across different UIs.