I wonder how feasible it would be to get a USB+headphone jack module. Like Dual USB-C Expansion Card - #320 by tbe, but with x1 USB-C and x1 3.5mm.
Although I guess it wouldn’t help with your desire for high-quality audio unless you could package a decent DAC into the expansion card, too. At first I was more thinking about the Framework 16 which doesn’t have an aux port at all.