This bug was fixed in the package grub2 - 2.04-1ubuntu26.2
--------------- grub2 (2.04-1ubuntu26.2) focal; urgency=medium
* debian/postinst.in: Avoid calling grub-install on upgrade of the grub-pc package, since we cannot be certain that it will install to the correct disk and a grub-install failure will render the system unbootable. LP: #1889556.
-- Steve Langasek <email address hidden> Thu, 30 Jul 2020 17:34:25 -0700
This bug was fixed in the package grub2 - 2.04-1ubuntu26.2
---------------
grub2 (2.04-1ubuntu26.2) focal; urgency=medium
* debian/postinst.in: Avoid calling grub-install on upgrade of the grub-pc
package, since we cannot be certain that it will install to the correct
disk and a grub-install failure will render the system unbootable.
LP: #1889556.
-- Steve Langasek <email address hidden> Thu, 30 Jul 2020 17:34:25 -0700