Just reporting back.
I pulled down the 9.0.9 release. Unzipped, had to run composer update and there are quite a few issues with dependencies, but with when I change it to use "node-sass": "~4.12.0", I can run npm install. When I run npm run build, it builds with no issues. I can see this in the main.css file:
@font-face {
font-family: "SocialIcons";
src: url(data:application/font-woff;base64,d09GRgABAAAAAA2UA...) format("woff");
font-weight: normal;
font-style: normal;
font-display: block;
}