I know a few boat in sites here in E. TN. Watts Bar lake, put in at the dam, on lake side. Cross the cove on the right, and then keep an eye on the right bank as you follow that bank. There are primitive sites scattered about.
Cherokee lake, put in at German Creek boat launch, head south toward main lake. There are sites on some of the islands.
South Holston Lake, near Bristol, put in at Hwy 421 bridge and head down toward dam. Allowed to camp on islands unless posted.
Maybe some forest service roads in the national parks allow some diverse camping, but I'm pretty sure you can only stay in certain spot for a limited time before you have to move.
I've seen very few drive in areas where a person can camp. Most end up getting trashed, and then closed off. The areas where people can pull in and camp for free are turning into homeless parking lots. Not putting blame to anyone that have fallen on hard times, even if they have made wrong decisions that put them in that situation, not for me to judge.
If you are homeless, for what it's worth, I wish you the best.