It looks like the 503 error usually means migration is in progress/Gitea is still initializing everything - https://github.com/go-gitea/gitea/issues/1772. Not sure is this is per-repo or per-instance of Gitea. Currently this is only happening on OpenShift.
Assuming it is per-instance when Gitea is installed, we should add a wait until Gitea is ready.
Create a repo and try to clone it until it succeeds?
It looks like the 503 error usually means migration is in progress/Gitea is still initializing everything - https://github.com/go-gitea/gitea/issues/1772. Not sure is this is per-repo or per-instance of Gitea. Currently this is only happening on OpenShift.
Assuming it is per-instance when Gitea is installed, we should add a wait until Gitea is ready.