Look, I once got everyone I know to switch to matrix (Riot, before element) and they depracated the client, made everyone redo their encryption keys, it was a huge mess. Nobody will ever listen to me ever again about a messaging app because of what new vector did with riot.

Matrix is too janky for people. Use something else. Simplex, signal, whatever.

Beyond that, the key is breaking this "one more app" mentality. Why is it so hard to have an app on your phone? These people would install the Starbucks app for a single free milkshake in a heartbeat. This expectation that everyone and everything can be done in one app is absurd, and it's marketing by the big companies to lock people in when there's no reason for it. your phone runs apps. What's the big deal?

And that starts with you. make yourself available on multiple different messengers as possible. Don't say "I use matrix", youre being inflexible. Use everything that doesn't collect your contacts and spy on you. Use telegram, but tell people telegram isn't encrypted. I personally have matrix, XMPP, session, signal, simplex, telegram, and I even have a discord but I never use it. I fall back to email if I have to. Be flexible if you expect others to be, be available to communicate with in as many ways as you can privately to incentivize people to switch, give them options and let them pick.