@Governor :-
What do the people who use other distros do for portable apps?
Mm. Well, technically speaking, AppImages, Flatpaks and Snaps all qualify as "portable" apps. I don't know how it is with Snaps and Flatpaks; both require a 'framework' to be in place in whatever distro you use them in. Snaps are a Canonical thing; Flatpaks are being more widely adopted by the greater Linux community, but due to the above-mentioned 'framework', I fail to understand how they CAN be considered 'portable'.
Both do contain everything they need to run, and their main claim to fame is that of isolating the app from the host OS by sandboxing it. This is true of AppImages, yet you can happily move an AppImage from one distro to another, click on it to run it and it should fire up. AppImages only require that fusermount be on the system.....'fuse' being an acronym for 'filesystem in user-space'. An AppImage creates its own 'virtual file-system' in /tmp for the duration, interacting with the kernel from that location.
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Common-place or not, the one thing all these different implementations have in common is creating a fresh batch of config files in every distro you run them in. Which struck me as incredibly untidy, since if you run a given AppImage in 20 different distros, you end up with 20 sets of the same identical config stuff.....which then gets left behind when you move on to another distro and take the AppImage with you! Plus you have to set it all up again from scratch every time you run it.....
In the Windoze world, these are catered for by the PortableApps.com website. And these have the right idea; the config stuff is also contained within the portable directory, so having set-up a PortableApp the way you like it, you can shut it down, unplug' em from the system - the recommended way to run these is from a flash drive - go to another machine/version of Windows, plug the drive back in again, fire it up and just carry on where you left off!
I did just this for my very last annual re-install of XP, more than a decade ago; instead of installing stuff as normal, I outfitted the system entirely with PortableApps. It was the smoothest, most glitch-free year I'd ever had, mainly due to the fact that PortableApps also contain their own 'mini-registry', and don't write to the system at all.....
.....and this is what I wanted to achieve in Puppy once I started experimenting, Fred having demonstrated it was perfectly "do-able" in Linux. An application you could run in one Puppy, shut-down, boot into another Puppy, fire it up again and just carry on with whatever you were doing....
I 'share' Puppy-portables between multiple Pups by running them from an 'external' data partition (my system has 2 storage drives; one just for Puppy stuff, and the other for pretty much everything else). You can achieve exactly the same effect by running them from a suitably-formatted flash-drive/external HDD/external SSD.
Mike.