Can Chosen Champion be changed between games in a match?

Ruling: Yes, Chosen Champion can be changed between games during sideboarding.

Nuances:

• You can remove the Chosen Champion entirely from your deck during sideboarding and replace it with a different color champion
• You can play both champions in your main deck and switch which one starts in the champion zone in games 2/3 without needing to sideboard
• The change happens during the sideboarding phase between games