Download the 20.04 arm64 image and save to an SD card. etcher works well for this
After flashing the image, re-mount the drive and copy the following files into <drive>/system-boot/
:
user-data
network-config
cmdline.txt
This can be streamlined with the following script: bootstrap-k3s.sh
:
./bootstrap-k3s.sh k3s-pi4-a /Volumes/system-boot
It will take some time for the cloud-init settings above to execute, so you may need to wait a while (10 mins?) before attempting to ssh into the newly-provisioned node. as the 'ubuntu' user. The new node should auto-join the k3s cluster.