The loopback command works just fine for me on Oracular's GRUB 2.12 UEFI build.
If anyone also is still affected on GRUB 2.12, please comment. ** Changed in: grub2 (Ubuntu) Status: Confirmed => Fix Released -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1851311 Title: loopback command hangs in 2.04 under UEFI To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1851311/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs