I'm not familiar with the Dragon other than Black Dragon, which is south. So I'm clearly not offering anything useful there.
You mentioned Ninemile, which AFAIK can be looped from East Carbon back to Wellington if you do the whole length. In that case you leave and return to US6/US191 in almost the same spot just 5 miles apart but do nearly 100 miles, a lot of which is dirt. Ninemile Road past Dry Canyon Road going east dead ends on the reservation or you can turn off midway and head north to Myton. I, like you I suppose, have not done anything other than US40 between Myton and Vernal. I've also never personally gone south from the Ninemile/Dry Canyon junction into Cottonwood Canyon along the WSA. Doing Ninemile itself is well worth the time, there's famously dozens of rock art panels and tons of archeological sites in the canyon.
en.wikipedia.org
Unless you mean a different Ninemile (9mile).