Fairy of Grass keeps a GitHub contribution graph green by committing for you. It’s a template repo: a GitHub Actions workflow runs once a day (~12:00 GMT) and pushes an empty commit, which counts as a contribution without pretending to be real work.
Setup is three steps
Create a repo from the template
Add one secret — USER_EMAIL — so the commit is attributed to you
Done; the daily schedule takes it from there
The whole thing is one cron-scheduled Action and a single secret — deliberately tiny, so it’s easy to read end-to-end before you trust it with your profile. (Whether you should farm your own grass is between you and your contribution graph.)