I managed to work around this like this:
* Forcing Windows 10 to use \EFI\ubuntu\shimx64.efi as in "bcdedit /set {bootmgr} path \EFI\ubuntu\shimx64.efi"
* Changing BIOS setup to use Secure Boot (Didn't have it, didn't want it. never had it).
Not both ubuntu and windows 10 boot correctly when grub menu shows up.
To answer my own comment #23.
I managed to work around this like this: shimx64. efi as in "bcdedit /set {bootmgr} path \EFI\ubuntu\ shimx64. efi"
* Forcing Windows 10 to use \EFI\ubuntu\
* Changing BIOS setup to use Secure Boot (Didn't have it, didn't want it. never had it).
Not both ubuntu and windows 10 boot correctly when grub menu shows up.