Have a look at Gitea. You can run it as a podman rootless container off the box on your local machine.
The functionality is there, the community refuses to switch. There people who still have the idea that gh is still whatvit was 10 years ago.
We did some profiling and spent quite a bit of time looking at Gitea's source code, it was pretty clear in the end that it's just very very inefficient for large setups. It does an excessive amount of I/O on the Git repositories every time you load a page; there is some caching but not enough / not of the right things. We were really open to implementing fixes and submitting PRs but the community was so hostile that we just abandoned it.
It was overall an enormous waste of time and I can't recommend Gitea to anyone with a setup larger than a handful of small repositories.
I wonder how CodeBerg works though.