Ubuntu will install perfectly fine on the G80 using UEFI mode. Do the following to install Ubuntu properly:
- Return the laptop to the original boot setting, not legacy
- Download Rufus to create the bootable USB drive (which works with UEFI and MBR)
- Reboot with flash drive connected (pressing F8 for boot options or F1 for BIOS setup whichever allows you to boot from USB)
- Install Ubuntu as normal (by creating custom partitions "only need root '/' and swap partition or '/home' if so desired") or choosing "along side Windows". This would be the quick way to get Ubuntu installed on the computer.
Also whenever you remove the partitions for a Ubuntu installation, because grub is installed you have to run a Windows installer to fix the boot for Windows. When you insert the Windows installation media choose "Repair my computer>Troubleshoot>Advanced>Command prompt". Run the following command:
This will fix the Windows boot loader so Windows boots right up after restarting, if you don't have something else installed that requires a boot loader.
I would suggest starting over with Ubuntu if you can to properly install it. Get booted up into the installer, remove the old partitions (not the Windows ones), and then recreating them again. This would ensure a fresh install of Ubuntu.