Another update. Being determined to be able to flash from an Ubuntu 22.04 machine I started digging into the scripts to see what they were actually doing.
It turns out the actual problem causing the mount.nfs: Connection timed out error was not the fact I was using Ubuntu 22.04, but rather just that the firewall was enabled and seems to be blocking the mounting of NFS needed for flashing. I disabled the firewall and the flashing worked from an Ubuntu 22.04 machine.
Hope this helps.