Just got the 2024 Prius Limited. I can't locate the sound buttons to adjust the music volume. Normally i'd find them on the steering wheel, and they are marked with a plus and a minus signs. The only option I know of right now is turning the knob on the multimedia panel. But it is inconvenient, and Toyota for whatever reason has placed it on the RIGHT side of the panel making it harder to reach, especially while driving.
The steering wheel has an up/down thingy (it's a little horizontal bar on the lower left with a tiny speaker icon, not +/- buttons). As I understand it, the dial on the right side of the multimedia panel is meant for the passenger.