This sass-based WP template is meant to serve as a very stripped-down, light-weight starter.

https://www.acegoulet.com/wordpress-starter-theme/

There are a bunch of default browser favicons and app icons included in the theme. Be sure to update these. Best resource: https://realfavicongenerator.net/

Run npm install on the theme directory then run gulp. All your Sass and JS assets should now be continuously watched and recompiled whenever you make changes. Look at the example files in /js and /sass. Everything should be pretty straightforward. Assets get compiled to /script.js, /script-min.js and /style.css. Remember to link your vendor and lib scripts and any additional js files in the js/main.js file in order for them to be included when the file is compiled.