Free continuous integration for private repositories

When you need continuous integration for a PRIVATE repository, what do you use? The 400 minutes of monthly GitLab CI pipeline build time don’t go very far.

For like 11 years I’ve been “full raw”

Repositories are simple git repositories managed by gitosis along with Jenkins CI running on the same machine and no github and no gitlab for years. Managing it on your own has so many advantages so I would most of the time advocate for it.