This is the same issue that is going on really heavily right now with Microsoft Accounts(and they are about to force the entire playerbase of Minecraft to give a phone number by pushing them to Microsoft accounts starting a day or two from now) (Note:This occurs without trying to use TOR during MS account creation, the system will lock you out afterwards- I assume TOR would be even more difficult)
To my understanding, even Protonmail has a odd requirement where you have to verify by making a donation, if you try to initially sign up with TOR- and sure, they might only keep a hash , but this is a risk as someone could generate a hash of all potential phone numbers and them compare.
Logging in via TOR afterwards to protonmail is good and all, but you aren't fully private then and can be compromised with out recourse it appears. [VPN would probably be the way to get around this][Protonmail is still probably the strongest option, especially since they won that court case they sued the Swiss gov in after being made to help the french government in that one case- now they are not able to be coerced at all - nontheless this signup TOR quirk is the only major thorn.]
I get the feeling no one realizes that you have these additional hoops to creating an account on any service- and that data they force you provide, could be subject to a subpoena in a jurisdiction where they don't like something you did, etc ,etc. And no, VOIP numbers and burner numbers are now auto-detected by these services and pre-blocked en masse.
I agree with another poster, Signal is probably okay in needing one, and they are working on removing that and providing unique identifiers at least, along with stripping as much metadata as they can. Other services seem to be going towards a point where you're at the mercy of whoever can compel or read the data they required of you to use services that did not require this.
I wish services would instead turn towards TOTP and other authentication, to avoid spam. The fact that that sort of substitute doesn't allow one to bypass giving up details like Phone numbers- suggests it's about the data, not authentication or anti-spam, since they offer no alternate.