As we have to build a flatpack application for each series. They must have each a different application ID in flatpack. But this means also that the Gtk application ID must follow the same schema in order to register in DBus.
So I propose to suffix org.tryton.Tryton with the series number prefixed by -. But as - is only allowed in the last part, we can not use . between major and minor version. So the result will be like org.tryton.Tryton-64 for the serie 6.4. This should not create any conflict because we never have minor release greater than 9.

Just tried to build it which ran fine, but version 6.2.4 was build instead of 6.4.0. I made some changes to the python3-tryton.json to download and install the right version.

Version 6.2.4 will start, but after filling the details and trying to login, it will crash. Version 6.4.0 however runs fine. I can login and do stuff without crashing. On the command line I get two messages:

Gtk-Message: 15:30:27.372: Failed to load module "canberra-gtk-module"
Gtk-Message: 15:30:27.372: Failed to load module "pk-gtk-module"

Can be a problem with my machine. I'm running Fedora 35.

It has been discussed on https://discuss.tryton.org/t/add-desktop-build-for-linux/927

review390041002 is an initial prototype to build flatpak for tryton-6.2.4.
It requires review390051002 because flatpak requires a minimum of 3 levels for the application ID (otherwise the DBus registration of Main application is forbidden as the root path is not the same flatpak application ID). Also the TMPDIR must adapted to allow other application to open them.

I propose to publish it on flathub but I do not know yet how to deal with the multiple series, so I asked on the forum: https://discourse.flathub.org/t/how-to-publish-multiple-major-version/2205.