I have a TempoTec Sonata HD Pro DAC (with CS43131) which works fine with my P6P since February update (i.e. when I got my P6P, so I do not know if it worked with previous versions ...).
I have also tried out some USB C to 3.5 dongles (from Essential, Xiaomi, etc.) and all of them worked.
I am aware that this may not be relevant for the more audiophile users here - I have read that some here are more concerned about LDAC at 990kbps ... When travelling I am fine with aptX HD or even SBC, and @ 127.0.0.1 I prefer cable bound audio transfer where my CS43131 DAC is sufficient. Just wanted to confirm it works.