How is this supposed to happen, please explain.
This device will do what it's supposed to do for several years, what's the reasoning for anybody selling it for 50 moneys.
People love standards and linux lacks a solid standard, there are as many versions out there as there are opinions about OSes, anybody can mix and match whatever they want, and while this is a great thing for people that do have a lot of knowledge it's the biggest horror for people that just need it to work.
Even just installing software is completely unintuitive and works differently on each system, if it's not in the depository a new user might as well forget about it.
SteamOs on the deck might be a good thing for that but then again they wont be able to produce enough units to make a dent.
While I agree there are many different Linux distributions out there, in reality only a few are "original" in some sense and all the others are basically "respins" of the original one, choosing some other defaults or tweaking the GUI. The respins work the same as the "original" so they are not that different. Basically these are the
major "original" distros, the rest are either based on these or very specialized distros not meant for Desktop:
Debian, Fedora (RedHat) , Arch, Gentoo
Ubuntu and Mint is Debian based,
SteamOS is Arch based etc.
Although Suse is its own distro it uses the same package system (rpm) as Fedora and is therefore very similar. An so on.
I agree though that the different mechanisms for handling installation of applications on Linux distros is a real problem that needs to be addressed. As long as the repository (kind of a software store) for your Linux distribution contains the applications you need and they are updated to new versions, then everything is fine and works quite well. The problem starts when the repository does not contain the application you need or contains an outdated version. Then it is handled in different ad-hoc ways which is neither good from a security perspective nor from a user friendliness perspective.
Personally I think flatpak has the best chance of standardizing packaging and distribution of applications across Linux distros:
https://flathub.org/home
The applications are kept up to date and works on all distros. The Firefox version is officially packaged and supported by the Mozilla organization. You should check it out.