After clean install of Zorin 16 on the HP Elitebook, I noticed a following error message appearing during the start up:
System BootOrder not found. Initializing defaults.
Creating boot entry "BootXXXX" with label "ubuntu" for the file "\EFI\ubuntu\shimx.efi"
Annoying thing is that it continuously adding an entry to the EFI, requiring clean up with efibootmgr tool.
I finally found a solution for this and I'd like to share it with others who might have this problem.
This procedure is based on a Youtube video: https://www.youtube.com/watch?v=GzObzq0V25A
open terminal, become root
$ sudo su
$ cd /boot/efi/EFI
backup BOOT directory
$ mv BOOT BOOT.bak
copy the content of ubuntu directory to newly created BOOT directory
$ cp -R ubuntu BOOT
$ cd BOOT
rename shimx64.efi to bootx64.efi
$ mv shimx64.efi bootx64.efi
As always, if you have any question please ask.