Does anyone know what theme is listed when you go here: https://about.gitea.com/
AFAIK, it’s a paid proprietary theme that CommitGo licensed to be able to use it.
However, the new dark theme in 1.22. should probably come close to this proprietary theme.
That screenshot was created for a proposal for the new/updated dark theme in Gitea. The project went in another direction for the new/updated dark theme, and so it was later repurposed. Although the new/updated dark theme in 1.22 that was just released looks just as snazzy.