I run it in a rootless Podman container using Quadlets. Instead of opening the server’s ssh port, I only port-forward the container’s ssh port (e.g. 22 -> 2222). I have sign-ups enabled, since I want people to be able to contribute (or just create issues). But I have configured the server so that nobody can create a repository. They can still fork my repos and send a pull request.
I have yet to experiment with Actions. I assume the safest option would be to only enable it for my own commits, but I am not sure.
I currently run it in Kubernetes but I just translated my existing Docker setup to it. I recommend setting up PostgreSQL and Redis if you can for the best performance, but SQLite and no-cache-approach is also fine for the beginning (you just run a single container).
That being said, I think Nextcloud is not very cloud-native. I set up Redis just so I can do rolling updates with zero downtime (filesystem locks are kept in Redis’ memory instead of the app’s own), but I still get some server errors for a brief moment during updates (for less than 10 seconds).