This particular example isn't very good, just install multiple kernels (or compile one yourself) on your distro of choice and boot into the one you want with your bootloader of choice. Once set up you don't even have to change any configs any more, just use an interactive menu on boot. So even easier than NixOS? There are plenty of valid use-cases for Nix, this isn't one of them.

[–] hisao@ani.social 4 points 1 week ago

just install multiple kernels (or compile one yourself) on your distro of choice and boot into the one you want with your bootloader of choice

That's way more complicated than adding a single line of text in a single text file and also having guaranteed way back if anything goes wrong.