To change the region in Legends of Runeterra you need to go through all the Challenges.
Legends of Runeterra How to change regions

After all Challenges are completed:

  • 1. Go to the Rewards section
  • 2. Click the Change Region button in the upper left corner.
  • 3. Choose region
  • 4. And click the Activate button
Legends of Runeterra How to change regions

We recommend that you receive the first 8 awards of all regions at the initial stage of the game.