I wondered how many Steam Decks are out there so tried to estimate based off the Steam Hardware Survey. TLDR - I estimated 448,000. As there are reports of over 1.5M sold as of May this year my method is clearly flawed. If anyone else has better ideas to estimate from imperfect data I would be interested.
On the Steam Hardware Survey 25% of Linux users GPUs match the "AMD Custom GPU 0405" which is specific to the Steam Deck. On all operating systems it is around the 53rd most common graphics card (irrelevant to the estimate). If you estimate ~140 million monthly active users (2021 was 130M, 2020 120M according to Statista
), multiply by Linux share of 1.28% and divide by 4 for 25% you get: 140,000,000 * 0.0128 / 4 = 448,000.
I've read that the rate of installing Windows on the deck is negligible so didn't include it.