Any progress on this one? While it only comes up occasionally, it's a major headache for me when it does.
That's the case for me today, when I'm trying to use my semi-automated system for sending out a couple of dozen emails. I currently have basically no choice but to use Chrome for this process -- even when I follow all of Apple's instructions and tell my Mac to use Orion for it, Orion has no clue what to do with the operation. (In practice, it winds up dumping the contents of the email into Kagi.)
mailto: is one of the oldest URL types, and still quite useful today -- it's a bit disappointing that Orion can't receive those links and direct them to a webmail interface like GMail or KagiMail.