Technically i've been paying for a voip line for 20 years, and shoehorning it into 3cx was mostly to allow my young kid to be able to call his aunt or someone who isn't on our PBX (grandma and grandpa and his siblings are, already).
believe me i was really annoyed when android stopped being able to reliably record calls. Another alternative that i did actually use is a 3 channel breakout connector on my cellphone, a DAC/ADC, PC microphone and headphones. You could tell the OS to "monitor" the microphone, and record mix (remember those days?). Or now-a-days you'd have to use VAC(virtual audio cable) or something to manage the routing. Speaker out goes to mic in on phone, and vice versa, hit record on your PC, and both the remote side and your side will be recorded. I never got too deep into this because it's a huge hassle unless you have a phone just for this; but multi-channel recordings would let you have synchronous audio, for, say, correct transcriptions.
Does anyone know of a reliable way to record conversations?