PXE secure boot install, out of memory for initrd

[mshapcotte]

I'm attempting to PXE boot (over TFTP) into the Proxmox 8.2-1 graphical installer.

This works fine with BIOS hosts using pxelinux from syslinux. I can build a menu, launch my choice of Proxmox version installer GUIs, etc.
This works fine with UEFI hosts using any modern grub EFI from, say, Fedora 40. I can build a grub menu, launch my choice of Proxmox version installer GUIs, etc.

With secure boot enabled, I can boot into the very same grub menu (same config as non-secure boot UEFI above) using the signed shim and signed grub that ship with the PVE 8.2-1 ISO:

• shimx64.efi.signed from the shim-signed_1.39+pmx1+15.7-1+pmx1_amd64.deb package
• grubnetx64.efi.signed from the grub-efi-amd64-signed_1+2.06+13+pmx2_amd64.deb package.

However, while loading the installer kernel works fine from the above signed grub (2.06-13+pmx2) I get an "error: out of memory" when it tries to load the initial ramdisk. (The installer boot process then proceeds a little bit before getting caught up on having no device drivers due to no initrd.)

I should mention that grub.cfg is specifying a decent ramdisk_size (which is working fine when being processed by other grubs on non-secure boot, just not the included signed grub).

Is there anything wrong (upstream bug, even) in the grubnetx64.efi.signed from the grub-efi-amd64-signed_1+2.06+13+pmx2_amd64.deb package? Or perhaps I've just not had enough coffee today and have missed something else...