Since Plexamp started receiving updates again, the interface reverted back to English and the language setting is gone. This is on iOS and I had the language set to Norwegian. Currently using version v4.50.19. The MacOS app however, still has the translations and the language option (v4.50.19).
Thanks, found it. When the mobile app moved to its new framework it stopped applying your language on iOS and Android, and the iOS build also lost the files that make Settings > Plexamp > Language appear. Both are fixed for the next beta, and once you’re on it the Language option is back in iOS Settings and Norwegian sticks.