In the Steam hardware survey, under Video Card Description, you can find: Steam Deck GPU - 0.45%.
Random sources online for which I cannot find a source (though I didn't really look much) say Steam has 132 million monthly active users.
If we take both of those figures at face value, assume being a monthly active user on Steam is a good proxy for "in use", then that makes 594,000 Steam Decks in active use.
This is far less than the sales figure that @breadsmasher@lemmy.world cited, which could be a combination of a lot of factors:
- Steam Decks which have been sold but are not in active use for whatever reason.
- The monthly active users figure for Steam seems low to me for a platform as big as Steam. It could be wrong.
- It is possible that Steam Deck users are under-represented in the Steam Hardware Survey, and they make up a bigger percentage of Steam users. Maybe they are less likely to participate in it?
- People might be using Steam Deck for other purposes besides Steam, so they are not active Steam users. Personally I doubt this is a significant factor.
- Some users might participate in the hardware survey more than once, causing the calculation to be wrong. I'm not sure how the hardware survey works, but this could be a huge factor.
- Who know what else I didn't think of.