Last week an update arrived in PureOS with improvements for #Librem5 call audio. You should be more legible to your interlocutors during calls; also, the phone now automatically switches to external wired microphone once connected. The whole audio path went through a big overhaul, allowing for hardware volume control with zero-cross and reducing unnecessary amplification that could cause distortions.
Haven't seen people complaining about the changes so far - that's a good sign :)
@dos Apart from getting this to work, I would be happy to test things to help pinpoint possible bugs. I am also planning to get a cash SIM card for my second L5, that is just now mostly resting on my desk. That way I can make L5-to-L5 calls too! :-)