I am currently working my way through this (free) course on music theory and can highly recommend it: https://www.daveconservatoire.org/
I’ve tried learning theory from a couple of (written) sources before and not got very far, and I’m not usually very good with learning from videos (they usually waffle too much for me!), but I’m actually really enjoying this - each video is only 5-10 minutes long, and they get straight to the point, but are presented in a nice informal way. The structure of the course mostly is good too, although there are a few bits that seem to appear out of order.
I’ve been watching a few videos before work most mornings and taking notes, I’m just starting on “modes” now and already feel much more confident in my understanding of what makes melodies work etc, despite not dedicating much time to putting it into practice. Definitely worth checking out I think