As noted on Reddit, Microsoft is offering a free month of Xbox Game Pass to new Microsoft Rewards members in select markets. We're not seeing the offer here in the United States, but our writer in France was able to sign up and receive the free Xbox Game Pass free code via email.
The offer appears to be tied to this link, which does not seem to be valid or working here in the United States. New users outside the US simply need to click on the link to sign up and then head to the Microsoft Rewards dashboard to redeem the Game Pass offer. Please note that the offer is scheduled to expire on February 28th, and you will need to give a phone number to verify your identity as part of the redemption process.
It's a bit rough to see that the offer is only for new accounts outside the US, but it is likely that Microsoft is just looking to promote the Rewards service with Europeans. Other users should keep in mind there are plenty of ways to earn points for Xbox Game Pass under the redesigned Microsoft Rewards dashboard.