I hope customer protection will eventually force new terms on the “you buy the rights to view a movie which can be revoked anytime without reason”. Like, given that most digital offers are priced nearly as high as their physical counterparts, there should be a law that the right must be given for at least 50 years or so.

Broken link? This seems to be a more or less up-to-date roadmap for Thunderbird on Android: https://developer.thunderbird.net/planning/android-roadmap

Self hosting your own CI/CD is the key for OP. Littering is solved too because litter is only a problem on long running servers, which is an anti-pattern in a CI/CD environment.

We use renovate mostly for container images and nuget/npm/maven dependencies.

If it’s relevant for your job, go for k8s. The more you tinker with it, the more knowledge you’ll accumulate. Is it the optimal solution for a self hosting setup? Well, it depends but most probably not.