Signal is a centralized app, run by a company. If they are offered enough money or legal threat they will sell out or close.
I am sure people will make an argument that its FOSS and people will just fork it if it goes bad, but a new fork will have 0 users and Signal will still have all of your old contacts. Why not make a switch now? Before it is even more popular and you have more reasons to stay? Why fork it if there are already decentralized apps that use same encryption, like XMPP apps?
Sure you can find flaws in every app, including XMPP implementations, but if we will have to write code for a new Signal fork, why not just fix whatever is that bugs you in XMPP clients?
If you want to use Matrix, that is fine as well, we can always bridge the two open protocols. But you cant bridge Signal if their company doesn’t allow it.
It might be a good idea to ask local schools to talk to every class about digital privacy, teacher might be into that. Telling them about examples, such as XMPP, might be very useful.
In theory yes that’s a good idea but sadly most teachers wouldn’t understand why we’d have the discussion and therefore not be super keen on randos wanting to talk to classes. And you need kids to actually want privacy when they post their entire lives online.