FWIW, OS/2 is actively developed, maintained for a price. I gather it's mostly for industrial control and ATMs these days.
I used OS/2 Warp 4.0 for a bit, when researching for my book on Windows NT. It's certainly not "DOS", or not only, as it's a protected memory kernel with DOS userspace. But it might be a DOS, or a direct descendant that has managed to swim all the way to 2022.
https://en.m.wikipedia.org/wiki/EComStation
And of course https://www.freedos.org
