Try Amber (amber-lang.net) - it's a Smalltalk implementation in JS and it doesn't use Morphic for display. It is, however, much less developed than either Squeak or Pharo; it may be alright for newcomers, but if you know one of the "real" Smalltalks, Amber falls rather short :(

The problem is that you either implement Morphic, which is designed to work on the level of pixels so you have to do it with <canvas>, or you don't and can then choose any display strategy you'd like. The problem is that Squeak and Pharo rely on Morphic for display, so you need to have it implemented if you want to reuse the code of those.

It's probably possible to write Morphic-compatible rendering framework based on React, for example, which would be an interesting excercise, but I don't know if anyone attempted it.