In my experience this doesn't work: switching. People will not do that. They just won't. It's the overwhelming majority that will not switch.
Maybe we need migration paths: let my FLOSS-chat talk to their evil surveillance capitalism driven chat.
I think that bridges are an important step to make people consider changing.
Today #fosdem at 6pm there are sessions about #chatmail and #deltachat and #webxdc ... Modern email devroom k.4.601 ... Happy global switch day :)