Updated: Dec 18, 2020
In all honesty the best way to learn is from a private instructor, (subtle name drop for my music school Avalon School of Music | Music School | Wylie, TX but in 2020, you will find the following channels are alive, and still posting excellent content:
JustinGuitar - Excellent for beginners who are just learning how to play guitar.
creativeguitarstudio - Has a nice course structure to follow, and teaches music theory.
Move Forward Guitar - Good basics course to follow, and nice strumming exercises.
Andy Guitar - Great basics, and good at teaching beginner songs.
Your Guitar Academy - Learning scales and more advanced songs; power chords.
https://www.youtube.com/channel/UCaiPnwW_X4IVEjWAmKf8OqQ/videos - Guitar at Work. Nice collection of more advanced songs and useful techniques.
Learn to Play it Right - Guitar Lessons - Playing songs with tabs and demos of the correct way to play songs.
GuitarLessons365Song - Great instruction for intermediate and advanced players. Hundreds of songs with on screen demos of how to pay.
New Secret Guitar Teacher - Intermediate songs, easy to listen to and understand. Some fingerpicking techniques.
Kelly Dean Allen Guitar - Plays through the top 100 guitar solos of all time (ranked by Guitar World). Lots of more advanced lessons.
Levi Clay - Advanced country player with multiple books on Amazon.
Chris Zoupa - Shred guitar. Enough said. Knows his stuff.
Rick Graham - Advanced modal and arpeggio style playing. String skipping.
https://www.youtube.com/channel/UCVD9PqYtkDkLUqKuzv4A5_Q/videos - Zombie Guitar. Deeper dive into music theory and its application to guitar playing.
Classical Guitar Shed - Just what’s written on the tin. Classical guitar from the intermediate player to advanced levels.