This is how people who lived before you did it. It's math. You can just read what they had to say instead of pretending a YouTube video or comic is actual hard won knowledge.
Nobody has anything more to say about Fourier series than what Walter Rudin figured out long ago. They can be defined for any locally compact abelian group. They are just trying to teach themselves about what is established theory.
As far as I know Rudin focuses on Fourier analysis on locally compact Abelian groups. There's been plenty of attention paid to doing Fourier analysis on other objects, especially compact Lie groups or symmetric spaces.
Of course there are people who would say that this isn't Fourier analysis anymore but the same ideas are still at play.
Fair enough. I'm just verklempt about the plethora of purported tutorials that barely scratch the surface. Sit down with a textbook. Read it. Think hard and do the problems. Watching cartoon animations is not learning the subject.
Excuse me, I've got a lot of clouds that need to be yelled at.
Nobody has anything more to say about Fourier series than what Walter Rudin figured out long ago. They can be defined for any locally compact abelian group. They are just trying to teach themselves about what is established theory.