As I wrote in this comment: https://phabricator.kde.org/R167:e3fad5256a5cba9f908f1f5d951907c6194040b5#896867
...I'd like to propose hard-coding proven mimetypes now missing from krarc.protocol.
I know they can be manually configured in Konfigurator -> Protocols, but I believe this is more convenient for users.