After applying that to GRUB and rebooting, I caught an odd screen I’d see a few times before (a gray screen with 3 square white dots). What I don’t recall seeing is the message “NVIDIA kernel missing. Falling back to nouveau”.
Since I have secure boot enabled, this has likely been an issue since the beginning. (Well, aside from the fact I didn’t have the NVIDIA drivers installed.) Imported the public key, from the README, message didn’t reappear. Hopefully that’s the root of my issues.