I just installed the following updates. Seems to have fixed the issue for me; grub-install now runs without error. Thanks very much!
Upgraded the following packages: libefiboot1 (37-2ubuntu2.1) to 37-2ubuntu2.2 libefivar1 (37-2ubuntu2.1) to 37-2ubuntu2.2 -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1872212 Title: grub-install: Operation not permitted To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/grub2-signed/+bug/1872212/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
