As a side note, I’ve found the “Automation” area of Localization Tools in Unreal Engine | Unreal Engine 5.5 Documentation | Epic Developer Community, but I could not find examples of implementing LocalizationProvider - I was lacking at least a single, very simple, but still step-by-step instruction/example, like "Let’s build a minimal super-basic LocalizationProvider that just imports everything from en.csv, de.csv, fr.csv files.
I guess I could read full code of XLocLocalizationProvider, but I felt that without any documentation of building it + not very extensive docs on UAT itself - it would be longer than a solution I described in the first post.
Maybe I’m wrong and should dive deeper in that direction.