These days, forest roads and primitive roads are often marked on Google / Apple maps and OpenStreetMaps. So asking your phone for directions to a national forest usually works well, as long as you check the camping rules and conditions ahead of time. You'll usually just see a series of pull-outs with fire pits and cleared areas along the unpaved roads.

Lands managed by the BLM or USFS usually allow dispersed camping in at least some areas, but it's still a good idea to double-check before you leave, and you should be aware that the same lands are often used for other activities like hunting, logging, horse-riding, grazing, offroad vehicles, etc.

You can also get more specialized outdoors mapping apps which can download data like USGS topographical maps and quad sheets for offline use. If you think you might like the backcountry, a satellite messenger is a good investment and those often have companion phone apps.

Don't forget to bring a big battery if you rely on electronics for mapping, though. And you can usually get decent paper maps from local NPS/USFS/etc visitor centers once you get to the area. The people in those visitor centers will also tell you where good sites / hikes / drives / views are, but then you have to actually talk to someone.

Also, read about pack-in/pack-out policies, what a cathole is, and how to keep your food from attracting animals.