After updating to Angular 12, it causes ng serve to fail with
Conflict: Multiple assets emit different content to the same filename index.html
Confirmed that the application still builds and runs properly without it.
This plugin isn't used by @angular-builders/custom-webpack since Angular 8 (see https://www.justjeb.com/post/customizing-angular-cli-build#viewer-51npg), this is just the first time it's actually causing problems for us.
Removed script-ext-html-webpack-plugin as well since that's an extension to html-webpack-plugin & can't run without it.