Retrieved via:
% cd templates/boot/addons/
% wget -q https://github.com/netbootxyz/netboot.xyz/releases/download/2.0.76/netboot.xyz.efi
% wget -q https://github.com/netbootxyz/netboot.xyz/releases/download/2.0.76/netboot.xyz.lkrn
% wget -q https://github.com/netbootxyz/netboot.xyz/releases/download/2.0.76/netboot.xyz-sha256-checksums.txt
% sha256sum --ignore-missing -c netboot.xyz-sha256-checksums.txt
netboot.xyz.efi: OK
netboot.xyz.lkrn: OK
sha256sum: WARNING: 1 line is improperly formatted
As of release 2.0.73, Grml 2022.11 works again, see
https://github.com/netbootxyz/netboot.xyz/issues/1310