Barton has such a module too, it’s what I based my circuit on though I used a different headphone amplifier. It takes up to 4 inputs and you can manually pan them between right and left. The circuit, though not the stupid layout/mechanical design, is here: https://github.com/holmesrichards/StereoOutKosmo . It does use one SMD chip (LM4808, SOIC-8) for the headphones.
NE5532 isn’t a “special chip”, it’s a readily available op amp, and if you used a TL072 instead you might not notice any difference. Or you might, I’m not sure why they chose it. Anyway, it’s $0.59 at Tayda.