That doesn’t make any sense as argument no matter how you spin it. Linux is the dominant system for servers for decades now, and a Debian Desktop is quite literally the same as Debian on a server except it also got a GUI of your choice slapped on top. There’s absolutely nothing obscure about it, neither did anyone from the kernel team (Linux), FSF (GNU utils) nor IBM / Red Hat (systemd & honestly way too much other stuff) etc. ever design something around STO. That’s a domain firmly situated in proprietary code since for FOSS it doesn’t make sense to begin with. The false errand of GRUB is the sole exception, well known and solved.

The desktop market share says absolutely nothing about what you’re trying to argue. Now if you were to argue that Linux is lacking in terms of desktop software isolation then you’d have a point, things like Flatpak still are addressing lots of issues. But to say “Linux” approaches security with obscurity is total nonsense.