> In my case there is a glitch in the 1903 install where having external drives attached forces a fail as the installer can't determine which is the Windows dri

> In my case there is a glitch in the 1903 install where having external drives attached forces a fail as the installer can't determine which is the Windows drive or something (per an error/forum I read at the time). All things old become new again. In the Vista and 7 era there were a bunch of updates that you just could not install if you booted Windows by chainloading its bootloader. You had to boot Windows straight from BIOS, otherwise they'd fail to install, because some obscure component in Windows couldn't figure out what C:\ was otherwise.