Upper lower done 4 times a week (2x upper 2x lower) is literally the perfect split. Enough time for recovery between workouts for both muscles and CNS, enough intra workout time to hit every muscle thoroughly without gassing out, everything gets hit 2x per week and you can hit it with quite some volume if you feel like it.
Just goated, full body 3x week is better in theory, but the moment you leave newb phase it's not enough recovery time.