Also, note that whatever Freedesktop SDK last shipped Python2 will eventually be EOL. I don't know what this means. Not sure if it eventually gets removed from Flathub along with all its dependencies. The consequence I encountered was getting spammed on package upgrades that I had an EOL GNOME platform installed. I removed the offending package because I didn't use it, so am not sure how long the dependency would have hung around.

I like Flatpak better, but for the purposes of maintaining Python2 support for as long as needed, I wonder if AppImages may be a better bet? You'd have to build your own Python, but you can then download and freeze all dependencies in a single binary. You may be able to do something similar with Flatpak, but the major benefit there is that you can get lots from the SDKs/platforms without having to vendor your own dependencies. It may also be possible to grab and freeze dependent SDKs into a CHIRP repository.