I recently did a project using Bootstrap 4, using vanilla ES6. Except for the modal dialogs - we couldn't figure out how to do Bootstrap modal event handling without jQuery (e.g. populate a model using an Ajax call when it's opened).

I actually like jQuery, but in this case it quite annoying having to have to bring it in where we needed it only for one tiny piece.

I'm sure we could have figured out a workaround if we spent enough time on it, but eventually you need to give up.

I even end up not including/importing the JS files, using CSS :hover/:focus-within dropdowns and :target modals