This just keeps careening around. Decided to try a SVGA cable and it works fine. Gets video to monitor, so looks like either the video card DVI circuit, the DVI cable, or the DVI port/circuit in the monitor has gone toes up. Will buy another DVI cable tomorrow and see if that is it. In the meantime, will continue with the SVGA.
That’s the good(?) news. The bad is that it has stopped dual booting and will only boot into Windows. So either,
the previously unused, but 2 year old SSD has crashed (it does not show up in Windows file explorer), or
the bootloader isn’t facilitating a dual boot.
The former seems the less likely (plus I am unsure how to test a SSD), so first how do I trouble shoot the bootloader?
EDIT: UPDATE: By pressing F12 during the boot process that now results in a Windows boot, a screen comes up:
Boot mode is set to UEFI with Legacy OPROM, secure boot off
Windows Boot Mgr (if selected, boots into Windows)
Ubuntu (if selected boots into Grub Screen and I select Ubuntu, it boots into UM18.04).
The good news is that (1) the SSD seems to be OK and (2) the grub screen is still there, bad news is that the computer does not boot into the Grub screen.
The other good news is that it narrows down what needs to be fixed, i.e., booting into the grub screen. How do I do this?