aaand more testing, did a full install with the stock iso, then ran with --unsupported after the install.
now i get "cannot download 32-bit grub packages, exiting".
Manually running "apt download grub-efi-ia32-bin grub-efi-ia32" fails, i had to run one apt download per file.
Those downloads are tarballs, one of them(the -bin) has the .deb file the script is expecting. the other one has nothing