Nah, they just come with their own external dac that plugs in with usb. The headphones themselves are 3.5mm.

They are super high impedance though so it’s probably safe to… pretend they are usb only unless plugged into some decent audio equipment. I wouldn’t expect much success plugging directly into a phone or something.

This project was started recently-ish and implies reverse engineering is the most important part. https://librephone.fsf.org/faq Haven’t seen much else listed out.