David Kimura PRO said over 2 years ago on Organizing Stimulus Controllers :
  Thanks! Personally, I still use webpacker as I have personally not experienced a lot of issues with it. It is a bit slow when creating new applications and from time to time do run into some nontrivial issues, but nothing that has forced me into a different direction. With the current version of hotwire-rails, both Turbo and Stimulus will install under app/javascript if you have webpacker installed on the project. 

I haven't tried using the ApplicationController for Stimulus on a non-webpacker app yet, but I'd imagine that it would work similarly.

I will probably continue to use webpacker for me applications until the Rails core advises for a different route. I think going the pure sprockets way will have some growing pains in modern Rails apps until there is a set standard way. It does seem like we are in a pre-transitionary period around this stuff, but this is my speculation and not based on any actual direction that I've seen. (other than hotwire-rails working with or without webpacker)