This is pretty close to how I did it.
The “one or the other” thing is a fallacy. You have just one, but they’re clearly happy installing stuff like WA - so tell them to install another app. It’s not like they have to switch.
If they subsequently come to realise the value of Signal in time, all the better.
I think you’ve misunderstood few things in my reply. I’ll clarify…
First, I meant the person with multiple IM clients will be the one who “doesn’t see the problem” with WhatsApp (or whatever). The person moving to Signal just has Signal.
Second, I wasn’t saying you used a fallacy. I was pointing out that when someone thinks of using (or are recommended to use) another IM client, they almost always think they have to uninstall what they’re currently using. (It is more accurate to call it a false dichotomy.) It’s a mystery to me why people think this way about IM clients, as many of us have multiple browsers installed, for example.
Third, my reply was about those you communicate with online, not you. Nothing in my reply was directed at you. 😊