I read the whole thread, and I don’t see much reasons to solicit their input. The problem was fixed, and when I install Portable Apps with Gramps here, Gramps follows all languages that I set in Portable Apps, like French, German, and English, and then back to Dutch.
This is a bit different from installing Gramps AIO in a Dutch Windows. With that, we had a problem where the installer didn’t read Windows’ language settings, and didn’t install any, so that Gramps fell back to its default language, which is mostly English. This issue was fixed some time ago, so now, with a default install, Gramps AIO speaks Dutch, and there is no easy way to change the language at run time. And even when I change some variable, it won’t speak German to me, because with default settings, only Dutch is installed here.
When you install Gramps inside Portable Apps, there is no dialog asking which languages and help files you want, and the fact that I can later switch languages at will suggests that the installer selects all. And since Gramps AIO comes with all GTK components that are needed, which are part of the OS in Linux, there is no need to install GTK language packs either. Gramps just works in the language that you set in Portable Apps, next time you start it.
One can argue that it would be better to have a language selector inside Gramps, or maybe more than one, so that I can run Gramps in Dutch, and create reports in English or German. But AFAIK, those are things that we can perfectly handle ourselves.
Note that on Linux, Gramps relies on GTK language packs, so when you change settings in Linux, with LANG, its behavior is different, and you may need to install the language pack first.