REGIONAL VARIANT EVOLUTION METHOD CHECK INS!
Meowth still evolves by happiness at night
Grimer & Diglett still evolve by level up
Pikachu cannot evolve into Alolan Raichu. Nothing is set up for it.
Slowpoke still evolves by the Galarica items, which are not currently available. I suspect they'll be available for purchase in the auction house, though I suppose we could have a dataminer double check? Otherwise we're just not evolving them until DLC unless an update coincides to home to add them to the pool. The items themselves are in the game ,at least.
Growlithe still uses Fire Stone
Voltorb still uses Leaf Stone
Sneasel still uses Razor Claw during the Day
Basculin still uses the recoil damage method (294 as a reminder). The initial set of data for Basculin-H accidentally pointed its evolution at an Egg, but they fixed that in an early patch.
Quilava, Dewott, Petilil, Rufflet, Bergmite, Dartrix cannot evolve into their Hisuian final forms. Nothing is set up for it.
Qwilfish-H, Stantler, Scyther & Ursaring cannot evolve into their new evolutions. They all share a unique, presumed placeholder, evolution method but it doesn't do anything at this juncture. Speculated that you'll get to do something with that in the DLC, but currently even once Home hits you likely wont be able to evolve them barring an update to the game. So uh, make sure you get an Overqwil before transferring I suppose.
Goomy is a bit of an outlier itself. Despite not having a unique final evolution and instead having the same "split" path that folks like Pikachu or Rufflet have, it does account for Hisuian Sliggoo. It uses the same "method" as the quartet but unlike them also checks an extra (unknown) Parameter.
Misread the situation, it has an alternate method that uses that placeholder with the Parameter check, but it's not directed to Sliggoo-H