Retrieved via:
% wget -q https://github.com/netbootxyz/netboot.xyz/releases/download/2.0.19/netboot.xyz.efi
% wget -q https://github.com/netbootxyz/netboot.xyz/releases/download/2.0.19/netboot.xyz.lkrn
% wget -q https://github.com/netbootxyz/netboot.xyz/releases/download/2.0.19/netboot.xyz-sha256-checksums.txt
% sha256sum -c netboot.xyz-sha256-checksums.txt 2>/dev/null | grep -e 'netboot.xyz.efi:' -e 'netboot.xyz.lkrn:'
netboot.xyz.efi: OK
netboot.xyz.lkrn: OK
See https://github.com/netbootxyz/netboot.xyz/issues/678