Ha, the 7070 problem is resolved as well. I tried installing and uninstalling the Audio driver and Waves MaxxAudio Pro multiple times, eventually it work! Not sure why, but not touching it again!
I bought 1x OptiPlex 7070 SFF and 1x OptiPlex 7080 SFF from different sources recently (and I have 7-8 other Dell, HP and Lenovo laptops and desktops at home, and I used to build PC's for fun, so I am not a newbie). Both 7070 and 7080 computers were installed with Win 11 Pro from scratch (deleted all disk partitions), updated with the latest drivers from Dell, and updated to the latest Windows update. Device Manager doesn't show any issue with any device. The problem is, when I plugin any headset, I can hear sound just fine, but microphone doesn't work!! This happens to both computers, and I have tried different brands of headsets, all with TRRS plugs that work just fine on other computers or phones. I also tried the front audio port and the back port (although the manual labels the back port as Audio Out only). "Microphone doesn't work" means the computer doesn't sense a mic has been plugged into the front audio port, so doesn't show my headset as a possible selection in various apps. I can verify this in Control Panel -> Sound, I have 3 devices listed: I assume... I thought I got a bad motherboard initially, but the fact 2 different models from 2 different sellers have the same problem makes me think I am missing something really simple. Can someone help?  
OptiPlex 7070 and 7080, front audio plug, microphone not working