if no application handling a particular mimetype is available but if this mimetype is aliased or a sub-class of another mimetype and if this mimetype is handled by a n installed application, xdg-mime query default will return no application.
Can you give a specific example of the failure, and provide which Desktop Environment you tested?
Closing, lack of feedback. Feel free to re-open if you can provide the requested information and/or test-case.
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