There are a lot of genres that fall into the folk category so I'll try to hit you with some variety.
Harry 'Haywire' McClintock - written around 1900, recorded 1928https://youtu.be/JqowmHgxVJQ
Merle Travis - 1940'shttps://youtu.be/s00MV1sY37c
Mississippi John Hurt - 1928https://youtu.be/24P8Q14yL94
Memphis Jug Band - 1928https://youtu.be/Z9-nW7U7qhI
Now for something new. This guy plays traditional blues and folk style, some standards but mostly originals.
C.W. Stoneking - 2015https://youtu.be/l9JXWhM8QXw
I'll throw in this Czeck folk song as a little bonushttps://youtu.be/5T_uxoV5FuQ