We bought a new computer and installed Fedora. I don't remember which release. I tried to configure the sound with the alsamixergui. No microphone detection, no matter what I did. I gave up.
I was encouraged to try again. This time I used alsamixer (not gui). There was a microphone selection option which I changed from 1 to 2 and voila, it worked.
Why didn't I see that before? I went back to alsamixergui and found the microphone selection option, but I couldn't see the setting, nor could I change its setting.
I sure hope this little bit of information helps somebody else.