Hi Vladimir,
I let our Jupyter people reply on that part. The plugins react e.g. to "TFile::Open(“myProtocol://foo/bar”) - you can register a handler for “myProtocol” within the TFile context. And yes, udev is a bad example because they have changes the location about three times, and distros disagree as much as possible with udev 
I said “for http: Jira ticket” and then, same line right after but different topic: “for html: that’s our old doc generator”. Sorry if that was confusing.
Cheers, Axel.