I tried to unpack an ISO of Ubuntu to USB stick without writing it (i can't use superuser utilities like dd or Rufus). Then i set my USB stick first in UEFI boot priority. I got working GRUB, but when i tried to run the system in live i got this error:
Initramfs unpacking failed: Decoding failed; Unable to find a medium container a live file system Attempt interactive netboot from a URL?
Maybe there is a way to run it from grub shell?