The phone number requirement is asinine and the reason I use Matrix, as I refuse to tie any identity of mine (even those I don't care about keeping private) to a phone number. Has Signal never heard of SIM swapping?
As I understand, that depends entirely on where you stand on the theory that the US government owns most of the exit nodes.
That said, the practical threat profile for most people is lower-level criminals and advertisers, so Tor is probably still a good idea in any case.
Do they? Their FAQ basically says that if your adversary is a nation state we aint gonna be much help.
I think they focus much more on anonymizing against ISPs and have basically thrown the towel in on defending against, say, correlation attacks by nation states.
Of course they have. Signal also has opt-in protection for that.
I can't edit my comment to correct it now, but in my defense Wikipedia says it's proprietary