I use Signal because there are few viable alternatives, but I absolutely hate that it requires a phone number at all. Nothing should require a phone number, much less use it as a primary account ID. Phone numbers are not user IDs. They do not belong to users, they can be reassigned to different people by third parties, they are frequently controlled by corporations with horrible security practices.

Ironically, iMessage is much better in this regard. You can actually use it with just an Apple ID, which does not require a phone number, only an email address.

It sounds like Signal will still require a phone number but merely allow you to hide it. That's a big improvement, but still bad.