The talented Andri Erlingsson has written Mounted Combat for Dungeon World and was kind enough to give me a peek. It’s really good.
From a design POV, most mounted combat rules for RPG’s tend to either be too fiddly or just boring, and this is everything but. You can ride BEES and sandworms in it.
There’s also a Mounted Combat & Vehicles for DW bundle available containing both Mounted Combat and Inverse World. So you get two for the price of well, a bit more than one. A steal. Inverse World is written by Jacob Randolph and Brandon Schmelz, who you might be familiar with. And Greg Stolze did a thing for it. And him you should know.
As for me, I think I need to go back to designing owlbears.