@elb this doesn’t match my experience as I’m running a CM4 here.
Which kernel are you using btw? I’ll using pkgs.linuxKernel.packages.linux_rpi4 which is a conservatively updated version of the raspberry pi linux kernel (currently 6.1, was 5.15 until recently)
If you’re trying to use a newer than LTS kernel I’d recommend using config.boot.zfs.package.latestCompatibleLinuxPackages which avoids accidentally using a kernel which wasn’t tested with ZFS yet