Network installing a Netra T1?

[Rich <rincebrain@gmail.com>]

Hi!
(Forgive me if this is well-answered somewhere, but I did some
searching, and did not come upon it.)

I have a Netra T1 running the old Debian sparc port. I wanted to
reinstall it with the sparc64 port, but it does not have a cdrom, and
I do not seem to grasp how to netboot the Debian installer for this
machine.

I tried just handing it vmlinux from
https://cdimage.debian.org/cdimage/ports/debian-installer/2021-04-17/sparc64/debian-installer-images_20210415_sparc64.tar.gz
over TFTP, but that just dies with "fast Data Access MMU Miss" before
ever displaying anything suggesting Linux was booting, so that seems
wrong.

I tried setting up GRUB using the config examples on the wiki, but
instead hanging it the vmlinux and initrd.img from the above
debian-installer tarball, but it just bails out into grub rescue after
printing "error: no DNS servers configured." (and I'm quite confident
my DHCP server is giving out DNS servers too), so I presume something
is going very wrong.

Any pointers or helpful hints would be welcomed.

Thanks!
- Rich