How to connect Mac M1 Mini iTunes OUT to an AV receiver?

I would like to be able to listen to my iTunes collection, acquired over many years, on my nearby audio receiver. I can't at the moment because the receiver came out before Airplay, and it doesn't do WiFi, and it doesn't have any inputs besides: Dual RCA jacks, Optical input, and S-video jacks. Period. No USB inputs, no Ethernet inputs. Meanwhile, most of the USB sound cards I find seem to be intended for the opposite purpose-routing audio INTO the computer rather than out. Can anyone help?