But still, to use it, you need a phone number, which in many countries can only be purchased with a passport. That’s the main rule. If privacy is really needed, personal identification should be excluded so that it’s basically impossible to determine who owns the account.

What kind of private communication can we talk about if you must have a valid phone number to use Signal?! Lol

Oh yes, these are indeed serious reasons to reconsider one’s view of Ubuntu.