BarryK, "Now we have Flatpak Installer".
esmourguit, "Would it be possible to get a flatpak for Gramps?"
BarryK, "Unfortunately, no:"
esmourguit "It's a shame."
It's not a shame. It's a blessing. flatpak is the "New Emperor's Clothes". Experiments with Puppy indicated that to install Flatpak required about a gigabyte of hardware space. That's for the 'framework' alone; sans applications. I'm posting from LinuxMint --don't ask why 
-- which comes with Flatpak. I just checked the size of the gramps flatpak package. It's a 1.1 Gb download which will require 1.6 Gbs of storage space*. The old deb version of Gramps was 6 Mb. Fleshed out with dependencies (unfortunately including python & modules) it's not likely to be more than a 30 Mb package. That's the size of the portable gramps.exe which will run under wine [albeit it complains about the absence of the open-street-maps module]. Perhaps less. Compare the size of the 'old' version created by muggins, https://oldforum.puppylinux.com/viewtopic.php?t=68580.
Currently my go-to web-browser is Brave. It's about a 100 Mb download, LinuxMint doesn't offer it. It now only offers Brave as a 250 Mb flatpak. My desktop has a reasonably powerful CPU and 16 Gbs of RAM. Optic Cables provide access to the internet. But it's two floors below the wifi router in a 60 year old building whose walls are solid so the wifi signal is at best --even with an extender-- about 40%. So while I have a reasonably powerful computer it faces a situation not dissimilar to that which those in third-world countries may have.
The first two attempt to install the Brave flatpak failed. After the 2nd failure I flinched MikeWalsh's portable and built a menu. I've done that with a couple other applications only available as flatpaks. But with Brave I persisted and was successful the third time. I don't pay for bandwidth. But how much was wasted by two unsuccessful attempts to download a 250 Mb package.
I don't compile: that requires learning a language and I lack that ability. So I can't say what problems might exist in compiling gramps. But instructions are available; it can be done and --except for python which I know nothing about other than it has its own quirks-- gramps compiling instructions don't seem much different than others I've seen.
But flatpak is a different story. At 1 Gb my suspicion is that it is too obtuse for all but experts. And that may be the worst thing about it. The spread of flatpaks discourages the creation of other packaging and distribution methods. It creates a new class: flatpak-experts. The incentive and opportunity of any who might be encouraged to learn how to create applications is minimalized.
Compare that to AppImages. Like flatpaks, a properly created AppImage contains all of an application's dependencies with instructions to use them. Their sizes are hardly more than those components. There are official tools with instructions for creating AppImages from 'sources'. fredx181 created an easy to use alternative which will run under any Puppy more-or-less creating a READ-Only rox-app or chrooted app. [TBO, the former is more likely to succeed than the later, and even that not always]. The problem with AppImages on the Web is that they are only tested against three major distros and, of course, not Puppys. So 'contains all' is an exaggeration. But you can extract an AppImage and employ the usual techniques under Puppys to determine what libraries are missing or other problems exist; and in many cases solve or workaround those issues.
IMHO, it makes more sense to 'normalize' the use of AppImages: provide tools for automating the creation of menus, testing for missing libraries, modifying them as necessary and repacking the modification.
-=-=-=-=--=-
* Considering that the framework-structure is 1Gb and the size of applications which use it far exceed the space required by the same applications not packaged as a flatpak, I'm wondering if flatpak is anything more than an unsophisticated containorization technique.
