I should mention I have ZFS on root, now:
ZPOOL_VDEV_NAME_PATH=1 pacman -Syu zfs-dkms
:: Synchronizing package databases...
core is up to date
extra is up to date
community is up to date
multilib is up to date
:: Starting full system upgrade...
resolving dependencies...
looking for conflicting packages...
Packages (1) zfs-dkms-2.2.0-1
Total Installed Size: 18.38 MiB
:: Proceed with installation? [Y/n] Y
(1/1) checking keys in keyring [##########################################################################] 100%
(1/1) checking package integrity [##########################################################################] 100%
(1/1) loading package files [##########################################################################] 100%
(1/1) checking for file conflicts [##########################################################################] 100%
(1/1) checking available disk space [##########################################################################] 100%
:: Processing package changes...
(1/1) installing zfs-dkms [##########################################################################] 100%
:: Running post-transaction hooks...
(1/2) Arming ConditionNeedsUpdate...
(2/2) Install DKMS modules
==> ERROR: Missing dev kernel headers for module zfs/2.2.0.
==> ERROR: Missing root kernel headers for module zfs/2.2.0.
==> ERROR: Missing bin kernel headers for module zfs/2.2.0.
==> ERROR: Missing usr kernel headers for module zfs/2.2.0.
==> ERROR: Missing run kernel headers for module zfs/2.2.0.
==> ERROR: Missing srv kernel headers for module zfs/2.2.0.
==> ERROR: Missing home kernel headers for module zfs/2.2.0.
==> ERROR: Missing mnt kernel headers for module zfs/2.2.0.
==> ERROR: Missing efi kernel headers for module zfs/2.2.0.
==> ERROR: Missing boot kernel headers for module zfs/2.2.0.
==> ERROR: Missing sbin kernel headers for module zfs/2.2.0.
==> ERROR: Missing var kernel headers for module zfs/2.2.0.
==> ERROR: Missing lib64 kernel headers for module zfs/2.2.0.
==> ERROR: Missing lib kernel headers for module zfs/2.2.0.
==> ERROR: Missing etc kernel headers for module zfs/2.2.0.
==> ERROR: Missing opt kernel headers for module zfs/2.2.0.
==> ERROR: Missing sys kernel headers for module zfs/2.2.0.
==> ERROR: Missing tmp kernel headers for module zfs/2.2.0.
==> ERROR: Missing proc kernel headers for module zfs/2.2.0.