Same with other translations without any maintainer. For example Swedish. I translate some parts for myself when I have time and share it.
In your case you can enable your Russian translation file.
- Download ru.po https://github.com/darktable-org/darktable/raw/master/po/ru.po
- Open with Poedit.
- Export/save/convert to darktable.mo
- Put darktable.mo in your language folder for darktable.
4a. WindowsC:\Program Files\darktable\share\locale\ru\LC_MESSAGES
4b. Ubuntu/usr/share/locale/ru/LC_MESSAGES
If you want to translate yourself you download the whole folder po darktable/po at master · darktable-org/darktable · GitHub and open up your ru.po in Poedit. Sync the file and start to edit.