I tried to revive an old mainboard from about 2005 with a #cyrix esther processor but all my current monitors failed to decode the #vga signal from it.
Only my lowest-quality 7-inch test-monitor showed the waiting BIOS screen, so I could proceed.

With an OS installed, new monitors work well with other graphics modes.
So it seems to be the boot graphics mode that is not supported anymore.

But why?
Modern display chips support so many features, why was backward compatibility removed? 😥