Thanks ovari for the version location 
So I have Build ID: 202509301457
NOW: GOOD NEWS!!!
It finaly works!
I checked several things, and what I spotted and changed is the output format for my usb dac/amplifier, I set it to the same format (24 bits, 48khz) as the internal sound card (so it matches the other computer default settings, both soundcard and webcam mic).
And now the sound is clear, the kind of saturation is gone! Even if commuting both webcams resolution to full hd.
→ This is great news. I guess thus that Jami itself cannot do format conversion (resampling)?
2nd question, important for group call (3 participants and above) → does it mean that all participants must have the same format (I guess it’s more the frequency than bits# that is important)?
It would mean that everybody needs to be in 48khz, for both webcam mic and sound outputs.
PS: I did a donation now, will see later for my family. I’m happy that it finaly works!