[2021] Purchased on different platform.

This is entirely dependent upon how you had preordered the game in the first place, but as the game is unreleased it should be easy for you to go ahead of claim a refund on it - allowing you to order it on the correct platform of your choice.

For example, if you had ordered it directly on the Xbox platform, you can request a refund on that item, alternatively, you could contact Xbox Support for further assistance. If you preordered the game with a retailer, you would need to contact that retailer.