Welcome to the forum!
As it's already been said, most breeds can be reliable trail horses, though a lot more depends on the individual horse's temperament and level of training. And, it also depends on the confidence and competence of the person holding the reins.
Many arena/show riders regard "trail riding" as something for people or horses who aren't "cut out" for anything else, but that's not exactly true. It's likely that the only trail rides those people have been on are just plodding down a wide-open, well-maintained path or going on a guided trail ride on a steady-eddy old horse.
They've probably never had to swim their horse across a flooded gully or slide down a greasy, muddy hill that was so steep the horse was literally sitting on its backside to balance itself.
Apps are popular as trail horses, so I think you're off to a good start.
Remember that horses are herd animals - there is safety in numbers. That doesn't mean you can't ride off alone, but you need to work on establishing trust with your horse and getting it to focus on you, not all of its "buddies" back at the barn.
You get a bombproof trail horse by practicing. There are some lessons that you can work on in the arena, like stepping over logs or weaving through cones. . .but there are other things that you can really only "practice" by putting in miles out on the trail.
If you can, find a riding buddy who has a sound, solid, seasoned trail horse and go out on rides together. My little black horse, Badger, became known as "Uncle Badger" at the barn where I used to board him because he was a great babysitter for younger horses when we went out on trail. Nothing ever phased him or spooked him, he'd cross any obstacle asked of him, and that helped to build the confidence of the less experienced horses and their riders.
Just take things slow at first.
"Parelli horsemanship is just like painting by the numbers. You need absolutely no skill. You just put this color here and this color there, and when you're done, you have ... a mess no one wants." mp