If their friendship relies on you installing an app on your phone, that's a very shallow friendship isn't it?
This argument doesn't make sense. You can't just ignore practical aspects entirely and justify it with a cheeky "if they're truely your friends they'll accomodate ahah".
Sure if I want to send a private message to a friend I don't care whether its via SMS or whatsapp, but if I'm in a group chat with 5 of my friends I won't send a transcript of the conversation to the one person who doesn't participate.
Or would you not want your friend to attend?
The choice is: do I want my friend to be included in my activities?
The choice is not: do I want my friend to be included and also send all of his data to some people I've never met?
Maybe it works for you, but not for most people.
I ring them up or SMS people.
I think your fear depends strongly on how open-minded/techie the girl is, though: I've used Signal to communicate with all of my Tinder contacts, but I will admit people remark on how it feels like a 'drug deal'.
I'm getting strange looks every day when people hear I don't use the platform. It's horrendous.
I also really fear for the moment where I've to tell a nice girl I met that I don't use the platform, and that we should use X other platform instead. I can imagine that to be a letdown or to be weird. That's insane to me.