I think part of the problem with a lot of "selling stuff on Linux" has been mucking around with different dependencies for the thousand different versions of Linux.
Historically, this has led to a couple solutions: either a) Just officially support one distro (usually Ubuntu), or b) just don't release a Linux version.
Flatpak has actually succeeded in making a system that kind of works everywhere, and I think it actually has a shot of being an equivalent to the Mac App Store.
Regardless of your opinions of GNOME and KDE, it’s hard to argue Flatpak has anything but good intentions, it’s made by people who want the Linux desktop to be better
This I agree with, but not this:
> and does actually do a good job of making "one package manager to rule them all".
That's not its goal. There are no terminal apps in it, so everyone that wants to run custom packages from a terminal is still going to need something like apt/dnf/homebrew.
I am reminded of that one game dev who dropped Linux support because 99% of their bug reports were coming from 1% of their total playerbase (read: the Linux crowd).
You can fork the base repository and just add the packages you want to have installed on your host system. Everything else is handled with flatpaks or with distrobox containers, or you could technically install whatever else package management system you wanted to.