Linux is our main OS. Every developer's workstation is setup on Linux. We develop on Python, Golang and Node.js with Redis, MongoDB, PostgreSQL & Elastic Search databases.
We develop native mobile applications on Android & iOS. We tried hybrid systems like phonegap, ionic, mixing web technology and mobile. But we weren't completely satisfied.
If you want mobile user get the best mobile experience we believe native application development is the solution.
Of course it almost requires twice the work since Java/Kotlin are totally different than Swift.
We started with Windows in 1998, then came .Net framework. that really gave us a lot of pleasure to develop again on Windows.
Since then we still work on some Windows projects for customers who are stuck with Microsoft or want to pay license for OS.