David Kimura PRO said over 2 years ago on Slim Select with Stimulus :
  rafal.siepak You may want to try and put the css imports in the CSS file. For example, using bootstrap with css-bundling, if I put the @use in the top of the file, it works.

@use "slim-select/dist/slimselect.css";
@import 'bootstrap/scss/bootstrap';
@import 'bootstrap-icons/font/bootstrap-icons';
@import 'drifting_ruby';