Head out 421 towards South Holston Lake. There’s a multitude of country roads off 421 to the North and South of the Highway. Cross the mountain on 421 into Johnson County and be prepared to go back in time 20-30 years. Remote southern Appalachian country as far as you want to ride.
Lots of locals also ride the Yuma loop, leaving from Yuma Elementary School near Kingsport. Reedy Creek bike ship in Kingsport does group rides throughout the week as well.

Perfect- thanks so much for the reply!

Sooo it’s my boyhood hom so give you Bit of local knowledge
South Holston dam has some nice road beneath the dam - the climb up to the dam is a decent test for the legs - view up top is spectacular - When I visit I usually go early AM - take you rod as some really good fishing beneath the dam / (Locals call it weir dam and you can google it) some big trout
Main road that takes you there has really wide berm but can be lots of glass since local like to heave bottles rather than put them in
The trash

Every Tues there are two shop rides. Both start at 6PM. One is at The Bike Shop in Johnson City, and the other starts at the Kingsport Aquatic Center (lead by Reedy Creek Bicycles in Kingsport)

Thursday night ride is called TNR and also starts at 6PM. Two options, either 28 or 36 miles. The longer route is usually the faster group. The shorter route is no drop. Both start and end at East TN State University (ETSU), and both also climb Buffalo Mountain (about 2.5 mile climb).

Saturday ride usually ends up being 60-100 miles and goes into the surrounding mountains. Usually a lot of climbing on a lot of low car volume roads. Super fun. Starts at ETSU.

Not sure where you will be staying in Bristol or I could suggest routes close to where you will be.