Installed Fedora Linux 40 in Nitro 5 AN515-58. When I plug in my headset, microphone doesn't work.

The issue with the headset microphone not working on your Acer Nitro 5 AN515-58 running Fedora Linux 40 seems to be a common problem. Here are a few potential solutions to try:

1. In Pavucontrol, go to the Configuration tab and ensure the Profile is set to "Analog Stereo Duplex". This activates both the microphone and speakers.
2. In the Input Devices tab of Pavucontrol, make sure the headset microphone is selected and not muted. The level bar should move when you speak into the mic.
3. Try recording a test audio file using the command arecord test.wav or arecord -f cd test.wav to check if the microphone is working.
4. Modify the /etc/modprobe.d/alsa-base.conf file with the following lines:

options snd-hda-intel model=alc287
options snd-hda-intel probe_mask=0x2

This may help the system detect the headset microphone.

1. Update to the latest kernel version (6.9 or higher) as some users reported improvements with newer kernels.

1. Make sure the headset microphone is not muted in PulseAudio Volume Control. Go to the Input Devices tab and ensure the microphone is selected and not muted
2. Try different headset models to isolate if it's a hardware compatibility issue. Some users have reported success with USB audio devices

it's possible there are still compatibility problems between your hardware and the Linux kernel audio drivers. In that case, you may need to wait for future kernel updates or consider using a USB audio adapter as a workaround