First you will have to disable hibernation and Fast Boot in your Windows 10 installation.
Boot into Windows, open command prompt as administrator and execute this command:
powercfg /h off
To disable Fast Boot open Control Panel (the old version - not the modern design),
select the Energy Settings, enable show hidden settings and uncheck Fast Boot.
Shutdown the machine (do NOT reboot) completely.
Reinstall the GRUB bootloader to your Ubuntu installation in EFI mode.
Boot from the Ubuntu install media - then open a terminal and execute:
sudo mount /dev/sda8 /mnt
sudo mount /dev/sda2 /mnt/boot/efi
for i in /dev /dev/pts /proc /sys /run; do sudo mount -B $i /mnt$i; done
sudo chroot /mnt
sda = disk |
sda2 = efi partition |
sda8 = system partition | (taken from pastebin output)
Boot into BIOS and change the boot order in UEFI settings.
Select Ubuntu to be the default operating system to boot.
Now you can select which system to boot from GRUB menu.
I recommend to not use any 3rd party tools as they may bring along issues in some time later on !