I get a window all the time saying “Warning: plugin XYZ has no translation for any of your configured languages, using US English instead”.
That’s cool, because I WANT the programme to run in English (I’d prefer real English, obviously, but American is good enough). How do I tell the tool that English is just fine?
In the About window, it also says: “LANG: nl_NL.UTF-8”, but while Dutch is my first language in real life, I don’t want Dutch language installations on my machine. I never said: “please install in Dutch!”
Your machine must have an environment variable setting “LANG=nl_NL.UTF-8”, possibly set by Windows or some other software. Gramps is using that to choose the language to display, but doesn’t have the translations installed for that language (some of the addons may have their own Dutch translations and have their output show up in Dutch).
To avoid Dutch and use English instead, you will have to modify that variable to LANG=en_GB.UTF-8 for your whole machine or at least for Gramps.
To do it in a startup shortcut, modify the shortcut Target to
'C:\Windows\System32\cmd.exe /c “SET LANG=en_GB.UTF-8 && START /D ^“C:\Program Files\GrampsAIO64-5.1.3^” gramps.exe”
The most idealistic situation is that the user is as facile in US English as the language selected for the operating system GUI on that computer. And that they would take the initiative to translate that Gramps feature for Dutch users who are non-English speakers.
Your situation is a bit different since you want the Gramps GUI to run in a different language than the OS.
(Note: I am a US English monoglot. But it seems odd that this warning is in English. So I will submit Enhancement Request 12087 that the Warning text be a flagged as a Target for Translators and that the name/path of the missing translation file be included to encourage Translations that would eliminate the Nag Warning.)