@Woody
FTV is not translated yet (which is on my todo list). But according to this discussion, you should be able to install any addon even if the translation for your language is not available:
In the get_addons function we get the list of preferred languages and add “en”.
Thanks for clarifying that!
addons-en.json
exists. So all the issues that people have reported with different languages (besides the labels being not translated) should be due to bugs or inconsistencies in core Gramps and I am relieved that I have not made any major mistakes in this regard.
Please note that this could be an issue with the addon manager:
Addon Manager still has immature parts.
[…]
There are a significant number of issues filed that were related to the Addon Manager. But since the code is not yet documented, @Nick-Hall is the only person picking up tasks for it.
According to the screenshots, there are many users who use different languages who haven’t reported these problems with the installation, so the problem may be somewhat specific.
If you are only experiencing this problem with FTV and no other addons that are also missing the German translation file, you can open a GitHub issue and we can try to narrow down the cause. Maybe your setup represents an edge case that the addon should handle and FTV doesn’t.