I have a few friends who put windows on the deck as an experiment. They mainly wanted to play their game pass games on Steam deck which honestly seems to be a cool combination. My deck is still Linux though. I have one friend who has been using Linux for the last 15 years on and off, waiting for it to become a usable desktop OS for them. I'm kind of in the same boat, waiting for Linux to be far less finicky than it is. I'm also waiting for the Linux community to become far better than it is. Anytime you seem to point out a problem with Linux you get a lot of backlash. It's been slowly getting better over the last 10-15 years but not very quickly. A lot of old guards who see any problem report as an attack on their very moral being. Arguing "Well I'd rather use Linux than be a slave to Microsoft!" or such. It's like my god, people are just trying to use the thing to get to the thing they really want to do. The thing that gets in the way less is the thing that wins.

Overall, I see more people keeping Linux on their Steam Deck than switching it to Windows but also see far fewer people switching to Linux on their desktops than people switching their steam decks to Windows. Both are incredibly rare cases. All of this is to say that while I really like Linux, I support Linux when I make my games, I don't see the majority of people using Linux as a desktop replacement until they fix some key issues with the community and general OS.

Your own friend group is the definition of selection bias, though - at the least, they know you and probably have similar interests/hobbies to some degree, and I daresay you've probably said something about Linux to them before.

And there's a whole, active subreddit for people who put windows on steam deck - apparently the initial problems people had with it have been getting ironed out more and more.

I don't know which is more common but I'd need to see actual data, either way.