In brief: Google has a three-month trial of Stadia Pro for YouTube Premium subscribers in selected countries in what looks to be a way to garner more players for its cloud gaming platform. If you haven't yet tried Stadia and have a YouTube Premium subscription, this is an excellent chance to try it out.
Google Stadia has been out for over a year and a half, receiving mixed reviews at launch. Google claims the service is "alive and well", though evidence suggests that things might not be as good as Google says. The service is starting to be supported by some TV models with Android TV, a welcome addition by all means, but not enough to make subscriptions sell like hotcakes.
However, to show its cloud gaming platform to more individuals, Google is offering a three-month Stadia Pro subscription to YouTube Premium subscribers, depending on where you live. This offer is only available in the US, Canada, France, Germany, Hungary, the Netherlands, Norway, Poland, Romania, Spain, Sweden, Switzerland, and the UK and for paid and trial YouTube Premium subscribers. However, you can't redeem it if you have an active Stadia Pro subscription or previously had one.
Canceling your Stadia Pro subscription strips you from any game you've acquired and any additional content you've claimed for those games with your Stadia Pro subscription. However, if you resubscribe to the service, Google will restore your library, including all DLCs you've bought.
At the moment, a YouTube Premium monthly subscription goes for $11.99. The Stadia Pro monthly subscription costs $9.99, valuing Google's offer at close to $30. Google's special offer is available until January 31st, 2022, but you'll be able to redeem it up to February 14th, 2022, at 9:00 AM PST or while supply lasts.