My experience: via iPhone 8 + Apple adaptor, it couldn’t drive big cans, and even for earbuds they lose significant volume. My phone has the 3.5mm jack, and it can deafen me. This matters more when hooking up to sound systems because it raises the noise floor.
It’s better than nothing, but it’s not good. I don’t know about the USB-C alternatives though - I can only hope they are better than the ‘lightning’ connector ones.