Just the mons that are newly introduced in legends. So a pokemon like pikachu can still learn the TMs/HMs a normal Pikachu can, but a pokemon like Hisuian Voltorb cannot learn any TM/HMs

And for pokemon that don't show regional differences until they evolve, they'd be able to learn TM/HMs while still in their unevolved form. But the moment they evolve, it's only tutor moves for them.