I think it was a dev of the reboot of Planetary Annihilation that said their Linux users / build made up a few percent of the sales but over 90 percent of all support tickets (!). Mind you that this was before Valve's Proton.
Edit: It was <0.1% sales but 20% of all support tickets: https://xcancel.com/bgolus/status/1080213166116597760
in other words, if you want your game tested and get good feedback for it, do release on linux. maybe even release on linux first. linux users will love you for it, and you get to release a more polished game for a wider audience on windows.
Compared to the dylib nightmare that Microsoft keeps shipping in Windows, native Steam/Linux is actually pretty consolidated.
Where I work now the top 10 customers are Linux shops. They probably account for 80% of our revenue. The remaining hundreds of customers are more evenly split between Linux and Windows.
So I guess it depends very much on what industry you're in. For consumer games it might be Windows, but outside of financials and administrative realms and into the world of embedded it's a heckuva lot of Linux. Support costs tend to be lower, and you really only have to target Red Hat and Ubuntu.
Even the "0.1% of sales" figure is quite atypical.
Linux users write highly detailed bug reports because it's the only way to get things fixed without coding the fix yourself.