[trash_panda]

There is no such thing as a "standard threat model". That's why the threat modeling concept exists in the first place, so you can adapt different solution to different requirements.

It is totally OK if you are extremely worried about hypothetical scenarios where the phone number you used to register to the Signal network can be correlated to your physical location and then a gas station camera filmed you and then all is lost; but I want to believe that really at risk people are smarter than that, and just get a burner phone and even pay a homeless person a few bucks to buy it for them.

There are also ways to get a phone number through the Internet, so you don't even have to go to a physical location to buy it.

I think that's why Signal isn't prioritizing this right now, phone numbers can be a problem? yes. Is it hard to get a fake phone number that is not traceable to you? not really. Next problem please.

I think Signal is achieving the goal of being the default go-to secure messenger. I'm sure, even technical people who like to nerd out on alternatives, faced with a real world risky situation when they have to communicate with a non-technical person, would recommend Signal without a second thought.