Well, maybe not. Solutions like GitLab and GitHub are much more than just Git Repositories. Their issue queue, merge request management, CI/CD infrastructure, etc is something that keeps you busy alone. I don’t think NC should get into this arena.
But I second the idea that NC may want to be hosted on a platform which follows the same ethics being OSS and user driven. Both has not been the case for GitHub even long before the acquisition and has been the reason for many to leave. Even the GNOME project shifted over to GitLab recently although there had been common leaders in both projects for many years.
Self-hosting GitLab is pretty simple and it sits very nicely next to NC in your own network. The community edition is extremely powerful and would most likely fulfill all the requirements out of the box.