The use, encouragement, and moreover requirement of a custom URL scheme "hkp" for keyservers is misguided. Since the keyserver interface is implemented entirely over HTTP, it should use the "http" or "https" scheme. In the past I could ignore this nonsense, as gpg would happily accept the "http" scheme. But at some point it began demanding that keyserver URL's have the "hkp" scheme. This is misguided because it prevents the exact same URL which is given to gpg as a keyserver to be given to a browser or anything else which understands HTTP. Most keyservers will rightly return an HTML form when you do a GET on the keyserver URL.
Accept the http URL scheme for keyservers once more, and discourage use of the hkp scheme.