I remember OS/2 by IBM which looked like Windows 3.11, and OS/2 Warp which looked like Windows 95. There were probably others.
Maybe GeOS/Geoworks?
It looked like this:

It was pretty similar to modern Windows but without taskbar or Start menu.
Instead, you had a main window called “program manager” with icons in it to start other programs.
Do you have any specific questions about it?What is that? I don’t think that’s what I had in mind. I think it’s DESQview I was trying to think of. Anyway, not important… it was just driving me nuts I could not remember.
Sorry, I think I misunderstood your question.
And I had literally never heard of any Windows 3 alternatives up to now.To be fair, I was quite vague. I think there are multiple right answers… but I recalled one starting w/a ‘D’ and that’s what I was trying to recall.
The first computer my dad bought, back in the late '80s, was mostly a DOS machine that also came with a mouse-driven GUI called GEM.
I don’t know if it ran on top of DOS, though. It booted directly from its own set of disks.
You might be talking about the DOS Shell. A pseudo graphical file managerm shipped with DOS.



