Well, fairbuds can be connected to my FP4 
.
The APP controls the sound level very well , and that’s IT 
The equaliser doesn’t work at all. … I … Don’t get it!
Best sound is with ANC on .
Edit : sound doesn’t align with video. Limits their use to calls (still needs to be tested & listening to music). Now I know why Fairphone is offering them for free. 