Gnome is considering to use GitLab CE. Git Hooks are available in that edition https://docs.gitlab.com/ce/administration/custom_hooks.html
The only Enterprise Edition feature that is under discussion is merging without creating a merge commit. We're considering to open source this to make this move work.
GitLab.com still feels slow but running an instance specifically for GNOME should be fast.
Yeah, it's interesting to see all the bad experiences mostly tie back to gitlab.com being shitty. I've run it self-hosted myself and have been extremely happy with it. Almost a totally set-and-forget experience too, assuming you don't care about those little updates all the time and keep it behind your firewall or reverse proxy.
Unless there's some special pricing, I don't see any of the enterprise options work out. You can't pay per month per contributor for a projects public bug tracker. So I'd think they'd stay with the CE and hack in/around the features they need.
Overall, I am very grateful that gitlab exists but gitlab.com does make me feel like gitlab over all is a slow piece of software.