I’m also a FP5 user, FP3 before that. Never had any problems whatsoever.

Used /e/ for a while on FP3, that was mostly fine but some annoyances like the camera being less good. So I switched back to stock android. Might try /e/ again soon though.

I haven’t had any problems with apps, audio, bluetooth, anything.

Yeah, no problems with Bluetooth and audio here. Wifi-reception is probably the best I ever had on a smart-phone.