Expanding on GP a bit, ssh is not just a core feature for SourceHut the _only_ allowed method of write access to a repository[0].
sr.ht does not support pushing to git repositories over HTTPS with a username+password — SSH keys are mandatory.
HTTP access is restricted to read-only operations (clone, pull, etc).
[0] https://web.archive.org/web/20231225152845/https://man.sr.ht...