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.
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.