Not really… it needs a HTML to load the polyfill and transform the XML

You can’t have the browser load an XML file and have it transformed automatically as happens now

Someone's already added a PR to allow exactly that. You just include a script tag within your XML file.

I'm sorry to bug you, but can you link up the docs / news / cite for that? Will they need to replace their XSL with some JS/TS/Whatever, or can you just stick a converter so the XSL gets interpreted as something legal? What do they need serverside?

I foresee a LOT of this "Panic Replace XSL" work landing right in my lap and if someone's already done the work I want to know about it.