So, I have a Threema license, but from what I’ve seen its encryption isn’t post-quantum. Signal’s encryption seems the strongest. I host my own matrix server.
Also, I kind of don’t care where the servers are or which provider it is. Everything is encrypted anyway.
Is it possible to use a number different to the one on the device you use? Seems like a simple workaround to use a throwaway SIM to set up, and then use it with that number moving forwards.
That sounds like an awful lot of work to workaround a problem that shouldn’t have existed in the first place.