Might be unpopular, but I'm super okay with maintainers just disappearing and ignoring their projects. Stop putting so much weight on the original package namespace. I know it's a lot of work, but in my experience, when maintainers disappear, the community creates a fork that's better maintained and people migrate to that version.

I think if you want to stop working on a project, and it's on github, just leave a note in the README, archive it and move on with your life. Don't give the keys to someone on the internet.