I just ran into the same issue yesterday when I was updating one of my machines. Furtunately I caught the DKMS error when mkinitcpio ran after the upgrade:

  ==> dkms install --no-depmod zfs/2.1.9 -k 6.2.8-arch1-1
  Error! Bad return status for module build on kernel: 6.2.8-arch1-1 (x86_64)
  Consult /var/lib/dkms/zfs/2.1.9/build/make.log for more information.
  ==> WARNING: `dkms install --no-depmod zfs/2.1.9 -k 6.2.8-arch1-1' exited 10

Issues like these are when being on a rolling-release distro might bite you.

To mitigate the risk a bit, I always have the linux-lts kernel package installed on all of my Arch Linux machines, which provides a fallback option when the mainline kernel fails, or some major kernel issue surfaces. In my case with the LTS kernel at 6.1.21-1-lts, DKMS build of ZFS on LTS succeeded, so it would have been a fallback option to boot even if I would have missed the error for the mainline kernel DKMS.

  ==> dkms install --no-depmod zfs/2.1.9 -k 6.1.21-1-lts
  ==> depmod 6.1.21-1-lts

I don't have my root on ZFS, I only use it for data storage, but if I ever did,I would make damn sure to build myself a live ISO with ZFS support and all drivers necessary for network access, ahead of time, in case I need to do an emergency repair. It doesn't need to always be on the latest kernel, just recent enough that you are able to mount all partitions and to chroot into the system.

For this issue a workaround with Kernel 6.2.8 is discussed in the AUR comments for zfs-dkms: https://aur.archlinux.org/packages/zfs-dkms This would involve editing the PKGBUILD for ZFS to patch the license for the symbols to GPL, though I'm not sure about the legality of this approach.