I have implemented the necessary automation to be able to update from Stretch to Sid in the CI pipeline of Entr: https://salsa.debian.org/debian/entr/-/blob/debian/latest/debian/salsa-ci.yml
There are multiple packages that are incompatible with skipping Debian releases, so there are multiple workarounds required. This package is however small so the minimal workarounds in the CI are pretty clean and will apply to any Debian system. I also use the same workarounds elsewhere but any larger package will need extra package-specific workarounds on top of this base case. Fixing this category of issues is hard, as most maintainers don't want to spend extra time on making all upgrades backwards compatible for past ~10 years, and the policy even states that Debian doesn't support skipping releases, so I expect we just need to document the workarounds and that's it.
