I came across this post by @wiak.
That was an interesting post - it was a bout a distro-agnostic installer for various portable apps (including appimages) out there. There are two variants, both by the same person:
1. https://github.com/ivan-hc/AM-application-manager (install system-wide)
2. https://github.com/ivan-hc/AppMan (install for a logged in user only)
At the time or writing, there are about 1800 packages you can install. Some of them are overlapping with that Fatdog provides in the ISO (or in the repo), e.g. libreoffice; but there are others which are not (e.g obs-studio).
I have packaged these two scripts into a single package, called "am-appman", and it is now available in the repo. You can install it using gslapt.
Once installed, in order to use it, you need to open a terminal and run the command "am" or "appman" (please read the links above to be very clear about the difference between the two). Run "am -h" or "appman -h" for help.
Caveats:
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0. Only works and tested with Fatdog64 901.
1. I have not tested installing all of these packages. I have only tested installing a few. I have also only tested the "am" version, not the "appman".
2. Many packages cannot be run as root. So you will need "run-as-spot package name". An example is obs-studio, abiword.
3. Some of the packages may not work at all.
4. Some of the packages are already provided by Fatdog in its repo, and in this case, it is preferable to use Fatdog's version (unless you really need the latest and greatest).
5. Note that the packages installed by am/appman are not official Fatdog packages. It is a binary packages installed from various sources; some are the official portable binaries (e.g. firefox), some are official appimages, some re-packaged binaries/appimages, etc. You may want to review the package sources if you're not sure where the package would come from.
Provided that you're happy to accept those constraints, then perhaps this can help to save your time if you need packages that aren't supplied by Fatdog. Another alternative is of course to use sbopkg, but that requires compiling; while the packages provided by am-appman are binaries (=ready to run, no compilation needed).
Note that packages installed by "am" or "appman" can be uninstalled, as they both keep track of the installation. They will only uninstall packages installed by themselves; they never uninstall packages installed by other way (e.g. by gslapt).
Have fun, and thanks again @wiak.