I dont agree. I tried to build and start the self-hosted signal for myself. As I know, version 5.1.0 of android app doesn't work with current server 3.21, but app version 4.66.1 works fine. I mean, app does not work as planed, of course you can write messages to yourself and send SMS, but you cannot find out if a user is registered number with a signal server and cannot start signal chat with him. All because of that, since 5.1.0 accesses /v1/attestation/<UUID> and gets 404, and 4.66.1 accesses /v1/profile/<number> and gets a valid server response.