Nope, can’t get these instructions to work in order to netboot Ubuntu 20.04.
First of all, if I use cdimage.ubuntu.com, wget insists on trying to use the IPv6-address, even though I don’t have IPv6, so it fails. If I replace the domain with an IPv4-address, it fails with “Network is unreachable”.
Something about the boot-process is doing something very wrong and it doesn’t help that I don’t have any way of telling it not to use IPv6. The fact that it insists on trying to use IPv6 and doesn’t fall back to trying IPv4 is definitely a bug.