Huh? Most FOSS desktop software is not commercial to begin with, however there are companies like JetBrains that do sell quite successfully to Linux users, even as their core product is FLOSS.
> It would be very interesting to know how many of those users has JetBrains actually managed to monetize on.
> developer tools, a very niche market
Overall yes, but on GNU/Linux, most users are still some kind of a developer.
I don't have numbers, but JetBrains did say that most users of their products use the paid version and that their Linux business is a healthy one. I am on Linux and subscribe to all their products and have colleagues and friends that do too, so we do exist.
I also paid for Githost.io when I was using GitLab.
In all fairness, developers have always mostly been allergic to paying for things. Even way back, when a lot of developer tools were proprietary and often had pretty significant price tags associated with them, the developer tools business was always a pretty tough one. Like open source software, the model generally worked best when the developer tools were effectively in support of some other part of the business. (Microsoft is a great example.)
JetBrains sells developer tools, a very niche market, specially when a large majority of FOSS is allergic to paying for tooling.
In fact I would bet a large percentage of those Linux users are using Android Studio or Community variants.
It would be very interesting to know how many of those users has JetBrains actually managed to monetize on.