Andrew Furmanczyk's "Learn Free Music Theory" is the best, in-depth music theory course offered on YouTube. It is long — over 18 hours long! — but Furmanczyk walks students through the very beginning of music theory to intermediate theory, similar to an introductory college course.
If you enjoyed Ableton's notation-less, rapid introduction format, then Casey Connor's "Music Theory Distilled" would be a great fit. Connor's course is similarly structured, covering Melody, Harmony, Rhythm, and Scales.
Musictheory.net is the most comprehensive music theory resource online.
Music Guru is a visual library to help practice and learn scales and chords on piano and guitar.
Advanced Topics - Learning Music
A short continuation of Ableton's course.
Introduction to Time Signatures
For learning time signatures.
For learning sheet music.