To add if using the 3.5mm adapter some require TRRS cables where some use TRS. The officisl Google one expects TRRS.

Also something to keep in mind that I haven't mentioned which may play a part in this, there's only digital USB-C audio on Pixels, no analog so your mic and/or DAC/Amp needs to be digital. Also when you do get it to work, volume can be low. Using an amp that can provide -10dB is advised also if you encounter it.