As you may know, there's a Gears of War: Reloaded beta running both this weekend and next, which you can join if you subscribe to Game Pass, have pre-ordered the game - or own Gears: Ultimate Edition.
And now several people, including Bluesky user Wario64, are reporting that Microsoft has started sending out codes to Gears: Ultimate Edition owners via Xbox. Be sure to check your DMs, and it seems that even those who have played the physical edition also received codes, although it was previously said that only those who had the digital edition were eligible.