direnv would have to do too many releases to keep up with all the other project changes

And then think about if you want a rolling release, or a fixed release. Although all the distros you mentioned are on the fixed release side.

Ubuntu 20.04 LTS

Canonical publishes new releases of Ubuntu on a regular cadence, enabling the community, businesses and developers to plan their roadmaps with the certainty of access to newer open source upstream capabilities.