Comment 6 for bug 1787692

Resolved my boot issue, I think. Errors on FAT32 ESP, my sda1.

Issue started with no space left on device.
Then I would add new UEFI boot entry for sda's ESP for 18.04, but on reboot UEFI would not use it, erased it and entries for all the .efi possibilities were added from boot device, my sdc.

Not sure if all fixes required, perhaps it originally was originally error corrupted fat32 ESP. But that error would keep appearing on reboot.

Reinstalled Asus UEFI, same version as one used since April 2018.
Unplugged all drives to get UEFI to reset, removed all entries from UEFI with efibootmgr.
Added UEFI boot entry for 18.04 using efibootmgr to to boot from sda1.
Every reboot, erased entry to boot sda, and only booted with rEFInd on sdc or external drive.
Ran fsck.vfat and it cleared error bit saying it may have not been umounted correctly. It is mounted with fstab in sda's install.
On reboot same issue, all UEFI entries for sda missing, and fsck.vfat showed error bit. I believe that is why UEFI would not use my sda1, ESP for booting.

Using another install so sda1, ESP not mounted.
Then totally reformatted sda1 using command line, mkfs, not gparted.
Updated ESP/efi entry in fstab in Ubuntu 18.04 install with new UUID.
Totally uninstalled & reinstalled grub signed version.
System now boots from ESP on sda again.