I kept a Docker install of GitLab running for many years at my first full time employer out of university back in 2014 to 2020. It was really not too difficult.

I kept a Docker install of GitLab running for many years at my first full time employer out of university back in 2014 to 2020. It was really not too difficult. Every once a while they would release a major version that required a migration or config update, but mostly the updates were a docker compose pull and docker compose up away. At our single company scale with only some 25 developers max (don't remember exactly anymore) a self-hosted instance on a moderate VM was super stable and quite boring. And boring is often good. It might be that hosting GitLab for much bigger organizations is a different beast! I remember that the first instance of their CI solution was a separate server/service that coordinated CI jobs on runners. That was a bit cumbersome. But then they integrated the CI coordination into the main server and you only needed to figure out the CI runner part. Today I would likely have gone for Forgejo with runners for such a small company if I were to self-host. Less moving parts and smaller footprint.