It's FOSS - https://itsfoss.com/linux-runs-top-supercomputers/
Linux might be struggling for a decent desktop market share but it is definitely ruling the world of supercomputers.
As per the latest report from Top 500, Linux now runs on all of the fastest 500 supercomputers in the world. The previous number was 498 as remaining two supercomputers ran Unix.
Top500 is an independent project that was launched in 1993 to benchmark supercomputers. It publishes the details about the top 500 fastest supercomputers known to them, twice a year. You can go the website and filter out the list based on various criteria such as country, OS type,