> But RHEL provides a supported way to install newer Python versions, so > this doesn't necessarily have to mean de-supporting a given RHEL version > altogether. I don't have an opinion on that at this time
That's possible on most (all?) platforms (pyenv/asdf/uv/mise/...). All with a question mark because I have no idea which of these would work on solaris, but some of them are pure bash scripts so those should work. (and that ignores windows, but that also shouldn't be an issue generally). These would be per user custom built pythons, so they would only work with the different plpython/pytest python approach, but would allow using the latest python for the test suite on all platforms.
