https://www.gamespot.com/articles/new-pubg-xbox-one-miramar-test-now-live-for-a-limi/1100-6458889/

Miramar returns for another round of testing in the Xbox One version of PlayerUnknown's Battlegrounds. For a limited time, players will have another chance to try the new desert map on console before it officially arrives later this month.

As before, anyone who owns PUBG on Xbox One will be able to participate in the Miramar test. However, you won't be able to get in to the test through the main client; rather, you'll have to download the PUBG Test Server from the Xbox Store, which will be available to everyone who has purchased the game.