I don’t really like Apple, but once in a while they do the right thing. This comes from the App store’s new labels on apps.
Signal just has “Contact info” under the “Data NOT linked to you” category. This is just the phone number + contact discovery.
UPDATE
There’s another post adding telegram here. This is what it looks like:
As far as I know, Matrix also has no data linked to you, as long as the federated instances you use and communicate with are running as intended.
There seems to be a bit more than with Signal. I guess is highly depends on which instance you interact with. Matrix encrypts less metadata than Signal and not all conversations are E2EE.
The difference is that phone numbers are tied to your identity, while email addresses are not (at least if you use an email service that doesn’t require a phone number).
Signal has mandatory phone numbers, matrix has optional ones.