The best Smalltalk is Objective-Smalltalk.
It's a beautiful way to go up and down the ladder of inference.
Basically—Objective-Smalltalk is based on Objective-C which is a superset of C. It's like having the two worlds coming together at the same time.
Does it miss some of the beauty of a totally integrated system like Squeak? Sure. But that's kind of the beauty too. Can we make an Objective-Smalltalk takeover?
I was recently re-watching the old demo of 280 North's Atlas, an Interface Builder-inspired tool. And when I think about it, it also seems a little strange that object lovers and all today's disaffected Mac fans could pick up the pieces of GNUStep and start building out a usable replacement for themselves as a reaction against the deterioration and inevitable demise of the Mac, but that isn't materializing. There's something, I think, in the Mac developer psyche that says they're responsible for building their own discrete little apps and doing a lot of polishing on them, but they're completely uninvolved in shaping or otherwise working on the environment/platform itself. This is the difference between Mac folks and Smalltalkers.
Necessity is the mother of invention! If the demise of the Mac / Cocoa API's is nigh—expect there to be some work on it.
This guy is doing some interesting work: https://mulle-objc.github.io
One more factor: my guess is that GNUstep picked the LGPL—which although more permissive than the GPL—turns away the money / status seeking Mac folks.
GNUstep has also moved to GitHub and seems to favor the the MIT license nowadays where possible (e.g., libobjc2)[1][2].