99% of flat earthers are just trolling, I refuse to believe anything else

The user land API/ABI is stable to a fault in Linux. The kernel API/ABI is unstable

It’s the other way around. The kernel API stable to a fault, the kernel ABI isn’t. If your application only relies on the kernel API you won’t have many compatibility issues. If you rely on userland stuff such as C++ stdlib, GTK, QT, Python, … Good luck.