Ah, through USB-C? That didn't occur to me.

Through an audio jack.

Mine do not have an audio jack.

What model do you have?

The five and era 100 both say they have a line in on the website.

I have two Era 100s purchased in December 2024. I have looked the entire thing over - if there is line-in, it must be through USB-C, there is no aux port.

Interesting, it looks like you are right, it is usbc:

https://www.sonos.com/en-us/shop/sonos-line-in-adapter