Here's the full distribution method list. Amazing that they're still doing the in-store-code thing during a pandemic
US, Canada, Australia, & Latin America - Through the Pokémon Trainers Club Newsletter. Sign up by November 20th to receive it in December
UK - GAME Stores (where open), GAME Online store soon
Germany - Gamestop - In-Store now, Online from December 1st
Austria, Switzerland - Gamestop - In-Store now
Italy - Gamestop Online Store
Spain - GAME retail, Online Store will add it soon
Belgium, Netherlands - GameMania - Sign up on their website, codes sent out every Friday
France - Micromania - Sign up on their website to get a code
Portugal - FNAC Stores
Sweden - Through Spelochsant or Webhallen's online portal
Ireland - Gamestop Website