Which pokemon from legends cannot have anything but a strange ball in scarlet
Unless I'm forgetting a quirk in ball passing via breeding...
Pokemon: Sneasler, Overqwil, Basculegion, Enamorus.
Stantler, Scyther, Ursaring can all obviously come in a variety of Pokeballs, be ported over to LA, evolve, and come back while retaining the ball.
Forms: Growlithe/Arcanine, Voltorb/Electrode, Basculin, Zorua/Zorora
The Hisuian starters, Sliggoo/Goodra, Avalugg, Braviary, & Lilligant get around this by bringing their pre-evolutions in from another game in a different ball.
Technically all of these pokemon, except for Enamorus, I think can also come in PokeBalls since if you breed a strange ball I think it just defaults to a PokeBall. Anything that's available in Go can also come in Pokeball, Great Ball or Ultra Ball (& Master Ball soon, I suppose). And obviously Zoroark specifically can come in a Cherish Ball.
e: Ah Nokocchi is right, you can pass the ball of either parent in recent generations provided they're the same species