InvisibleInk
Headphoneus Supremus
Tested it.
Controlling playback or volume with a 3.5mm remote cable doesn't work on TempoTec V3. Neither does it on HiBy R2 II.
So, most likely - HiBy OS related.
Thanks again. It was mentioned on HiBy and Shanling threads a DAP needs to include hardware, probably some IC, to enable the cable playback controls. My older R3 Pro could do it, and there is a setting to enable/disable it. I guess HiBy did away with that feature on newer DAPs like your R2.
Unfortunately for me, my R3 Pro has somehow got stuck on its balanced 2.5mm phone out, so I can not use my 3.5mm port any more.