Okay, for those interested, the hardkernel image of Ubuntu 22.04 Minimal with linux kernel 4.9 does not work well with zfs. Following the advice from here, I instead installed another community image of Ubuntu 22.04 from here. See the discussion here for more info on this image. It is not official, but stable. This image comes with linux kernel 5.15, which is one of the the latest linux kernels that work with ZFS 2.1.5. ZFS 2.1.5 is what is installed from 22.04 on this image, so everything seems to work.