I started with
Mark Williams Coherent Unix in the early 1990s and it had twm. When I moved to FreeBSD 2.0.5 in 1995 Xfree86 defaulted to twm and I was happy. I'm still happy
twm is nice and lightweight (very few dependencies), very snappy and infinitely customisable.
That said, when I was running Solaris on my work machine at a previous employer, I quite liked CDE which did have workspaces, but it was on the heavyweight and sluggish side of the equation and back in those days my monitor was just 14" whereas today it's 24" and can fit everything I do on one screen easily.