I don’t , I’ve never run one.
The closest thing was that I ran a challenge mode dungeon or two with a guild group back in MoP and didn’t even really care for that which is one of the reasons I know that I would really dislike M+. The go,go,go situation in normal/heroic dungeons is bad enough even without the timer that I usually avoid those too.
My previous comment is not a complaint but an explanation, it just makes it so that Mythic + isn’t content for me and that’s fine.