Hello, I'm currently in the process of contributing localization to Turris OS which also has LuCI on it. Turris OS (as well as other notable FOSS projects) use Weblate to streamline localization. For example, you need only create an account to contribute; one doesn't have to worry about learning Git, finding and learning a tool like Lokalize, etc. Then there's also other useful features like getting notifications when a .po is updated, translation memory to easily see how similar strings were translated in order to keep consistency, etc.
It would be really nice if OpenWrt followed suit so I could easily translate Turris and LuCI, and so practically anyone who speaks two languages can easily contribute! Since OpenWrt is FOSS, Weblate could do free hosting for the community as well!