Okay so this is actually due to the entire loopback file being measured and only shows up with the TPM enabled, there was a bugfix posted to grub-devel, so likely not actually fixed until Ubuntu has shipped that.
** Changed in: grub2 (Ubuntu) Status: Fix Released => Confirmed ** Summary changed: - loopback command hangs in 2.04 under UEFI + loopback command taking too long with TPM enabled -- 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 taking too long with TPM enabled 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