I haven't used Android since Nokia 7 Plus (back in 2019) but the variant that I had back then (TA-1062) doesn't have Japanese locale settings, despite being Android One and all that. I had to install MoreLocale2 and modify the settings via adb to make it work.

Every phone that was sold in the region I used to live (SEA) also lacks Japanese locale out-of-the-box. I had assumed this was still the case (locale availability tie to region being sold).