As for languages, kodi-languages will not solve the problem I mentioned in the bug [2]:
> Kodi will auto-install 77 (assumedly all) language addons automatically. > I am unable to remove them in the kodi addons interface, only disable > them. Uninstall is grayed out. If I try to delete them from ~/.kodi, > they just auto-install themselves again. I'm only interested in one > language addon, en_us and the rest really clutter the addons menu. > I can't find a setting anywhere to choose or stop this
Your proposed solution is no different from current one as majority of Kodi users choose non-English locale. I tolerated it for 20.x series but I'd strongly prefer to have language packs separated in 21.x onwards, similar to libreoffice etc.
FWIW: I added one more d/copyright fix for 21.1 clarifying licensing of skin.estuary [3].