Credit to @Kaizuken at MyDealz and heads up to @merb086 for the spot.
Info translated and paraphrased from MyDealz
Xbox One / Series X/S players can buy the game for £4.99 and subsequently gift the game twice to other users (Note - you can only buy the game twice as a gift because it has a cool down timer of 24 hours).
1. Add the free Weekend game to your library i.e. Call of Duty Free Weekend.
2. Buy the Cross-Gen bundle upgrade for £4.99, or give it away!microsoft.com/en-…tab