I have been trying to Install 18.04.3 in dual boot mode. My latest attempt is to install on a USB memory stick of 128gb. The install ends with an error message basically saying "Cannot install Grub".
I ran the install from an Ubuntu Live USB stick with the main hard drive removed, so the only drive available for install was the 128gb USB.
The only success I have had is to an old Hard Drive running from a USB connection. However, there are errors even so and the performance is far too slow to be useable. Hence wish to run from a fast USB. An attempt to upgrade to Kernal 5 killed the working Ubuntu 18.04 I did have on a separate partition of the main drive.
Does anyone have any ideas to fix, please? PC Boot is via UEFI and the main drive (when connected) is a Samsung SSD which has Windows 10 on an encrypted drive.