Helmut said almost 4 years ago on Autocomplete with StimulusJS :
David, I got it working! 

I removed the Yarn install of autocomplete, and then installed again. Nothing. Finally, I came across the "application.js" file in a "javascript/packs" folder and noticed that it had some of the same lines as the index.js file. I had used this file to install Tailwind and Flatpickr a couple months ago, but that was about it, and I forgot about it. But it occurred to me that index.js is being ignored because application.js  is doing all that stuff already. So I just moved the "import Autocomplete" and "application.register" lines into my application.js file, and everything worked....

Whew! 

Thanks for the assistance, though, it's appreciated....