Fixable with browser extension
"Trivial"* fix with a browser extension** from someone like EFF, where the extension sends the start_url (with no other user information) to a central server. If the server sees a high proportion of unique start_urls for a particular second-level or top-level domain, it responds that there may be fingerprinting going on, and the extension can warn the user.
* Relies on user installing extension, but the same is true of pretty much anything of this kind, including Privacy Badger.
** Assumes a browser extension can examine (but not manipulate) such requests. If not, perhaps the browser manufacturers should consider that extension point.