I got the exact same error after upgrading from Ubuntu 19.04 to Ubuntu 19.10 on my HP EliteBook 820 G4. Disabling TPM in UEFI "solved" it for me. Seems to be a bug in grub2 package version 2.04 in Ubuntu 19.10. Seems they added UEFI TPM 1.2/2.0 support to grub2 version 2.04 in July 2019, but it obviously does not work for us.....
https://www.phoronix.com/scan.php?page=news_item&px=GRUB-2.04-Released -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1848892 Title: "error: Unknown TPM error." after upgrading to grub 2.04 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1848892/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
