Am starting a new thread for the new Radeon? AMD Caicos adapter I have installed because the on-board Matrox cannot cope with newer OS.
Having switched to the add-in card in the BIOS the booting process proceeds as usual but when the system offers the selection of starting and I select Leap15.3 system I get the black screen. This is what happened with the original card which I had put aside believing it broken, but now I have the same problem with replacement card. What next?
Perform fresh install and compare results. You made too much changes to run Matrox graphics.
OK but that is a major investment in time. Could I use the repair installation?
Everything was written to you: https://forums.opensuse.org/showthread.php/556873-New-Installation-Display-Configuration-and-Resolution-Problem?p=3050824#post3050824
and previous messages.
I found I had a DVD so didn’t need the time using the net installation but…
I had set the BIOS for the Add-in adapter and now the boot DVD gives me an Out of Range black screen so I cannot do a new installation using the analogue connection.
Went over it all again. Moving the computer to a new location I had used a new cable. Never checked before but not all vga cables are created equal. The one I used just happened to have a missing pin.
All that time and effort and it was a cable fault. A new cable solved the problem. Blushes and apologies all round.