`config.boot.zfs.package.latestCompatibleLinuxPackages`
That way the main maintainer can still follow HEAD, whilst the ZFS maintainer can make sure that Linux is updated for ZFS once it’s been tested (or even automatically, but I don’t know if it’s that advanced yet).
At the very least you can take a working copy and figure out exactly which configuration is necessary. Hard to do that without NixOS. Especially with nixos-option.
And the options are all documented in a central place. The module definitions using the options are also “easy” to search through (Language is a bit complicated, but not in a way that grep doesn’t work).
Well, on any system there are tons of sneaky config options that one must get right to get a working system; it's just that on non-nixos, those aren't deterministic/version-control friendly/reproducible/centralized.