While technology marches ahead, some products are slow to upgrade and require some backward compatibility. I'm sure you've heard about the demand for COBOL programmers in the US during the pandemic.
I often work with a platform that still adds charset=iso-8859-1 to the header of each page. 😔 This creates a few issues with new SASS/SCSS and JavaScript compilers, as they render output in Unicode by default, regardless how the source was written. The problem I ran into is that I would use ASCII code in source content: '\2714'; and the compiler would outputcontent:✔;optimizing things for me by converting ASCII to Unicode. The problem would come when the CSS is rendered on the page, the desired checkbox would not appear. I've attempted adding various iterations for @charset rule at the top of the CSS, which did not help.
I did some digging round and found the issue in Dart Sass repository that has been open the last 5 years; seems I'm not the only one running into this problem.
The great folks in the discussion pointed me to an already existing solution for Webpack. In my instance, I was working with Gulp. So I've created a Gulp plugin that did the same things in the Gulp framework. This allowed me to use the new SCSS and new Dart Sass compiler and not worry about the old school character sets on pages.
Hope you find this helpful.
P.S. Attribution and big thanks to styzhang for the main solution with an MIT license.