There are lots of mountain bike trails around Tucson, some of which can be easily ridden on gravel bikes. In general I try to note which trails are okay on a gravel bike. Some of the trails are part of trail systems, such as Fantasy Island, McKenzie Ranch, Sweetwater, and so on. Others are single trails, such as parts of the Arizona Trail.
Still others are jeep roads that are also good mountain bike routes. I’ve generally tried to write about these rides in the Dirt Road pages. So here I’m mainly focusing on singletrack riding. However I’m not much concerned with hard downhill rides because I don’t have the interest, skill, or courage for them
MTB Project is a fantastic web site for finding mountain bike rides. It has an associated app you can download to your phone, which is invaluable when doing rides that have confusing intersections. The app is well worth downloading. Really. You can also download .gpx files of the rides from the web site.
Caveat: I’ve only been riding the mountain bike trails around Tucson since November, 2020, so the list of rides and areas shown here is sparse. Hopefully it will soon expand.