There is already a thread about the microphone not working during calls. However, that thread dealt with issues such as the hardware switch being turned off, or the use of an unstable alpha version of Gnome Calls. I have a similar problem, but I believe it relates to permissions for apps to access hardware, rather than to the issues in the existing thread.
[EDIT 4 March 2023: Hardware permissions are not the cause. Various other suggested causes are disproved in this thread (including theories about network configuration). So far there is no further suggestion beyond those that have been disproved. One fact that has been established is that audio can be sent from the Calls app to the SIP server in the form of DTMF tones before a call is connected (thus enabling calls to be dialled), while neither microphone audio nor DTMF tones go from the Calls app to the server once the call has been connected. One user does report two-way audio on a VoIP call from Calls on his L5; so far only the one user has reported this success, while several others report one-way audio only.]
Possibly this merits an entry in OS-issues. Advice from more experienced users would be welcomed.
With settings for my VoIP provider in the Calls app, the app works beautifully, except that there is no outgoing sound. (No problem with ringing whether for incoming or outgoing call; the ringing stops as it should when the call is picked up. Incoming audio is high quality and smooth.)
(I have not tried Calls on a cellular network and do not intend to use the Librem-5 for cellular calling in the country where I live.)
The hardware switch for microphone and camera is turned on.
In Settings>Sound>Input>[Handset Microphone - Built-in Audio]
the indicator line of dashes responds strongly to sounds, showing that the microphone can communicate with the OS.
Downgrading to 43-beta version made no difference. I have reverted to the latest 44-alpha.
The contents of Settings>Privacy>Microphone suggest the possibility of a Permissions problem. The following two paragraphs appear there:
“Use of the microphone allows applications to record and listen to audio. Disabling the microphone may cause some applications to not function properly.”
“Allow the applications below to use your microphone.”
Below those paragraphs there is a box with the further message:
“No Applications Have Asked for Microphone Access”
It appears that there should be a drop-down menu of apps, or some facility for writing the name of an app (specifically Calls in this case) in the box, to allow the app to use the microphone. However, those things do not exist on the page, or anywhere else that I can find in the GUI. I am not keen to delve into udev rules to fix this problem.
I have a vague memory that, during the initial setup 7 weeks ago, there was a question about app permissions for mic and camera. I may have opted not to allow access, assuming that this could be easily reversed. That does not seem to be the case.