Do any trainers use Unown in their teams at all?
I define core as any Version [whatever] games. No console games count.
Yes, but it’s unlikely you’ve ever met them.
You might be familiar with the Trainer Hill found in Pokémon Emerald, but it’s a little known fact that connecting the e-Reader to a Japanese version of Pokémon Emerald lets you add trainers to the Hill based on which cards you’ve scanned. Two of these trainers, Pokéfan Francisco and Pokéfan Kimberly, can, depending on whether their cards were scanned first or second on a floor, battle using 3 different Unown each.
For the international release of Pokémon Emerald, Pokéfan Francisco and Pokéfan Kimberly can be fought on the 4th floor of the Trainer Hill’s Variety Mode, where they will, again, both have a team of 3 Unown.
In Pokémon Crystal, Unown can be randomly fought in the Battle Tower’s level 10 challenge, but it’s never fought again in any other similar attraction in later games.