Well, I took the mirror apart (I practiced for when I will put smoked blinkers).
I can confirm that those lights are indeed led lights. Wiring seems fine. Front and rear turn signal work ok.
Manual says turn signals fuses are F25 and F26 on fuse box in engine compartment. I checked those and they are fine.
Last think I need to check is if I didn't accidentally turn them off with VAG-COM, although I wouldn't have any idea on how to check that. Controller 9? Controller 46? Which bit should I look for?
I doubt it is a VAG-COM issue, if I did turn them off by mistake why would the right one work and not the left one? Unless they can be turned off separately through adaptation? But at this point that would have been too complicated an operation to have been done by mistake.
Looks like I gotta take a trip to the dealership. Man, I hate that...