Thanks for all the replies!
I don't really need left and right audio separately, I'll probably set the output that I'm using for the led effects to mono and then simply use either the right or the left channel since they are identical then. I don't want to use a microphone because then it will pick up sounds from the room and not just the audio signal I care about.
I was hoping to calculate the peak volume in code by taking the highest value of the last 3 seconds or so..
I'm pretty bad at reading circuit diagrams, did I wire this up correctly?
I'm kind of scared attaching this to my audio equipment. Is this safe or could I break something by accidentally shorting a wire or something?
That ESP32 project looks interesting. I might take a closer look at it later, but for now I'm trying to keep it simple.