Ubuntu 16.04 can't install GRUB

Hi GVS and welcome to Askubuntu! I believe I see the problem: You haven't created an EFI partition! This partition is where the installer will place grub during installation on a UEFI system, but without that partition, grub can't be installed. To fix this, we will need to re-partition your drive. Please follow the steps below:

1. Open a terminal and type gksudo gparted (ifgparted is not installed, then you must run sudo apt install gparted, first). Once gparted is open, right-click on each partition and click "Delete".
2. Create a partition 300 Mib in size, formatted as FAT32.
3. Create your other partitions as normal.
4. Right-click your first partition (the one formatted as FAT32), choose "Manage Flags", and then click the check boxes for "boot" and "esp".
5. Lastly, click the "Apply All Operations" icon near the top of the window.

After following these steps, you may run the installer as normal. Please let me know if you need any further assistance :)

I had the same problem. Following the advice of @user311982 with a twist, I was able to install Ubuntu 16.04 from the installation media. Follow the normal installation procedure(s) until you are presented the options to install/overwrite/side-by-side/do-something-else the installation. Choose "Do something else". From there you can select the target installation, revert the partition table (remove partitions) and then create a partition with the "EFI Partition" option. My assumption is that this essentially does what @user311982 was saying about "boot" and "esp", but was simplified. Since you removed the existing partitions, you will want to use the remaining disk space for your normal "ext4" partitions.

Then just proceed as normal.