@tadziuuu Just to be clear on a few points.
The .iso / memdisk route only works for bios based computers. This will not work for uefi based computers.
With the .iso image files and the parameter block I previously provided, you get the error message about initramfs? If yes, then I suspect the fetch command is not downloading the squashfs filesystem. I copied that command over from your initial parameter block. It looks like we need to focus on that bit then.