Question: how to get all three starters in pokemon sword without trading?
Answer: You'll send one of your Pokémon out and in return, get a Pokémon from another random person. That Pokémon could be anything from a Magikarp to an Intelleon, and you have no control over it. If you don't have any friends to trade with, this is probably the only way you'll be able to get the starters.