> There's also the fact that Ubuntu ships with the GNOME desktop environment, and really only GNOME.

This is a feature. Standardization is what makes „Works on Ubuntu“ a stable target.

I also dislike Snap and the various other Ubuntu anti-features, which is why I recommend Pop OS - at least I did when it was a light weight Ubuntu fork, it may not be anymore.

This is just a rando‘s opinion, so it may not be based on that, but my intuition from a few years ago is that Debian/Ubuntu still has a reliable lead in the availability of software packages, especially less popular ones: You’ll almost never find something that doesn’t work on Ubuntu, for other distros this happens sometimes.

Has this changed? Maybe with the widespread adoption of Flatpak this is not much of an issue for consumer apps anymore?

yeah PopOS has been getting kind of weird lately