Isle of Armor:
In the Isle of Armor, you can have a choice between Squirtle and Bulbasuar that are both capable of gigantamaxing. Venusaur, Blastoise, Gigantamax Venusaur, and Gigantamax Blastoise can be found in raid dens.
The alolan starters are available by finding Digletts around the Isle of Armor. If you chose Sobble, you get Popplio. If you chose Scorbunny, you get Litten. If you chose Grookey, you get Rowlet. These always have their Hidden Abilities.
Crown Tundra:
Blaziken, Sceptile, Swampert, Marshtomp, Combusken, and Grovyle can be found in Dynamax adventures.