Network Booting LXD Appliance Cluster on Raspberry Pi 4

There was a nice tutorial by @stgraber on LXD Cluster using appliance image.
Is there a way to ditch the sdcard and network boot RPi4 using that image ? It would be great to be able to run the cluster using a NFS server. Appreciate any pointers.

I already tried changing the cmdline.txt providing it an nfs root however after fetching the u-boot from tftpboot server it just hangs. The initrd.img does seem to have local and nfs scripts, I was not able to figure out how to trigger mounting root from nfs server.