I have a GitHub pages website that uses a custom domain.
The domain serves a webapp made in Angular but when I access my domain the .js and .css files are not loading and on DevTools/Network I see a 404 Not Found per each .js or .css file I have on the branch assigned to the GitHub pages domain.
It's a common problem in Angular. When you generate the bundles you need to use:
ng build --prod --base-href ./
to set base-href to the root folder containing the bundles. Or if you already deployed the project just edit index.html and change the base tag to
<base href="./">
More information in the docs.