I’m having the same trouble with 18.04. Was curious if you found a work around. Booting the ISO itself works fine, but PXE booting doesn’t work. My guess is that the network, obviously, has to start sooner in order to pull over the files via NFS, and this is somehow mucking up the traditional order of operations.

@Wayne-Workman That is much more elegant than either of my solutions. I doubt you will need my help, but give me a poke if you want me to look at anything with you.