Author here. In the article there's some evidence that Ember is still at least talked a lot about in Rails job posts. Maybe I'll look into that more the next time I do this kind of digging.

Personally, I made a couple of attempts to learn Ember. Though it was well documented and looked great, I just bounced off of it both times. And I never had an urgent need for it, so...I eventually found Stimulus easier to pick up.