> Every company I've been at that tried to self-host something like GitLab, later moved to GitHub

Interesting, my experience has been the opposite. 99% of companies I've seen self host their VCS, it has been Gitlab (with some rare sel-hosted GitHub Enterprise everyone seems to hate, and the very rare Bitbucket).

To be fair most of them started with it when Gitlab was really really ahead, features wise. The gap has somewhat closed, but Gitlab is still a superior product IMO. Just the fact that you can have an actual organisational structure, and move it around, and share variables/configs between groupings, beats anything GitHub have to offer which is slightly nicer than GitLab.