I didn't know this was possible, but apparently you can now use Signal anonymously.
This is enabled by using publicly available phone numbers together with a new "Registration Lock" feature which prevents re-registering such a phone number (since users don't own them) and thereby stealing the account.
https://community.signalusers.org/t/how-to-use-signal-anonymously/2277
@jeroenpraat As far as I understand the procedure, you don't need to be in the US or Canada. You will get a US or Canada phone number to use for Signal, yes, but that doesn't matter at all. It's just a random number.
@natanji Oh yes, you are right, it's a virtual number, like this one: https://smsreceivefree.com/info/13433035367/
But how do we know that number isn't used by another person? Oh well, it is used (as I can see on that page), so probably it's helpful for some people.
@jeroenpraat That's the point; it might be used by another person, but each number can be registered for one Signal account as well, and said account can then be locked to disallow any modifications/another user taking over.
@natanji
I can't find the registration lock feature. Is it newer than my version? Old and gone?
@natanji
Answer: newer than my version. Whoops!
@natanji Only in the US or Canada, and not very easy to do. Better to use #Wire.