Setup Page Needs Disclaimer

The Set Up Flathub page is not an exhaustive list of distros that support flatpak/Flathub, but it doesn’t say this anywhere. Can we add a footnote saying “This is not an exhaustive list. Consult your distro’s documentation to see if/how you can set up Flathub”? It will prevent people from assuming Flathub is unavailable on their distro just because they don’t find it there.