Looking back, corporate-sponsored FOSS projects seem to be somewhat at risk of getting abandoned (Gerrit by Google Inc. not atypical?). Did you consider and evaluate "grassroot-movement", community-driven Open-Source alternatives like Gogs or Gitea, so that future development does not depend on a single commercial sponsor? Platforms like NotABug or Codeberg.org seem to prove that these are approaching maturity and scale easily to several thousand repos and would easily meet the requirements listed above. Have such alternatives been discussed and evaluated?
Topic on Talk:GitLab/2020 consultation
I'll preface this by noting that I use Gitea personally, and find it to be pretty good software. That said, though this consultation is specifically about whether or not to use GitLab for code review, we initially evaluated GitLab in the context of looking at alternatives for our continuous integration system, and that's still a problem we need to solve. Gogs/Gitea is essentially a lightweight replication of the GitHub-style code forge, not a platform with components like the full-fledged CI system that motivated us to investigate GitLab in the first place.
The shorter version of this answer is: Not really, but not for lack of awareness.