> Or will this always just be user error! you're doing it wrong!

I suppose this is what my reply will boil down to, but also isn't that fine? You could do something unusual on macOS or Windows and there too throw your hands up in mock shock that it was to be labelled 'user error'.

Anyway, when I want to install software on Linux I type `yay -Ss software` (on my work/personal machines) or `apt search software` (on a Debian derivative image) etc., and then install what I've found similarly.

Thunderbird could do better here - greenfield software today might offer a Snap or Flatpak package there for example - but I don't think download via vendor website is the norm on any distribution; it tends to work on macOS & Windows, but is decreasingly primary even there; it probably could launch Ubuntu Software Center (or whatever it is) as it does App Store.app on macOS - but who wants to look up what to do and maintain everything like that for N top Linux distros?

If it were me I think I'd just have a dummy button, conveying somehow that it 'works on Linux, you should refer to your package manager'.