> Linux has a stable system call ABI

This is a noble but practically worthless ideal. Hardly anything is written against the kernel ABI except glibc itself. End-user application developers don't write against the kernel interface. Platform library and application developers like KDE and GNOME don't really write against the kernel interface either. Nowadays even driver developers don't entirely write against the kernel interface, instead also linking in glibc and lib{std}c++ for things like shader compilers (which is nowadays usually just a fork of Clang). Like it or not, glibc is the singular entry point for desktop Linux, which is the point of essentially every comment under this post.

That 'desktop Linux ≡ glibc' is something that I daresay the kernel developers also have to take responsibility for, rather than shrugging their shoulders and pawning it off to GNU. Linux's unstable user-mode is the entire reason for Docker's existence. It is bodge upon bodge and has led to much gnashing of teeth. The GNU/Linux community (I don't care for Stallman's meme rant here) have to grow a backbone and understand that an OS is much more than just a kernel, it is a platform, and currently the Linux platform is a disparate set of communities with highly divergent goals.

That's why I've always said the best Linux is Android, because Android is a platform.