Well, I don't know kCFI being enabled on any distro besides Android, cause it requires building the kernel with Clang.

The previous in-kernel CFI implementation (before the kinda joint effort - kCFI) was upstreamed by Google, too: https://www.phoronix.com/news/Clang-CFI-Linux-Patches and https://www.phoronix.com/news/Linux-Kernel-Clang-LTO-Patches. Pixel devices also had this long before. Given that the entire Linux kernel feature was developed out of Android I find it a little bit unfair to call it "using a vanilla kernel feature".