Well, I and a lot of the people I'm going to talk to through things like Signal are going to have a state ID regardless as I live in a country where one practically needs to drive a car to function in society.

On top of that so many other things just inherently expect one to have a phone number. It would be somewhat odd to not have a phone number for most of the people I know and talk to through platforms like Signal.

So to your question of which is easier, having the state ID and a phone number is easier because I'll already have that for a multitude of reasons.

If you live in a place where its rare to have a phone number, then yes I agree Signal probably isn't a good choice.