Verification-done for xenial, using shim-signed 1.32~16.04.1:
I have verified that interactive, non-interactive (old dkms update) and non-interactive (new pulled update) behave correctly: interactive package installs always prompt the user, non-interactive installs attempt to prompt the user but can't due to running non-interactively, so they fail the unattended upgrade in the case where a new DKMS package is being installed, or continue (without a failure, but also not promting, along with a notice to that effect in the logs) on successfully.
Verification-done for xenial, using shim-signed 1.32~16.04.1:
I have verified that interactive, non-interactive (old dkms update) and non-interactive (new pulled update) behave correctly: interactive package installs always prompt the user, non-interactive installs attempt to prompt the user but can't due to running non-interactively, so they fail the unattended upgrade in the case where a new DKMS package is being installed, or continue (without a failure, but also not promting, along with a notice to that effect in the logs) on successfully.