Sorry to laugh first off (more of a giggle really) but I just finished a 4 WEEK stretch with the same issue. I know you pain (if you have formatted at LEAST 10 times with various options).
- Disable secure boot. Install.
- Enable secure boot. Install.
There should be an option menu after pressing a key during boot up that gives various devices to boot from
(Selecting the option with EFI: / UEFI: disables secure boot)
Fix for me: Download and run boot repair.
This is also included in ubuntu-secure-remix (non-official ubuntu)
I wish you the best of luck.