How can I troubleshoot a headset microphone and unstable Ethernet connection on Linux Mint?

For the microphone, try another headset or microphone first to determine whether this is a Linux configuration issue or a hardware/connector compatibility problem. Also check that the correct input device and port are selected in pavucontrol, and make sure the headset’s combined audio/microphone plug is fully inserted. If tapping is detected but speech is not, the input may be using the wrong microphone profile or port.

It may help to test the connection with another Ethernet cable or router port and compare it with another device on the same network. When it fails, check the interface state and assigned address with commands such as `ip addr` and `nmcli device status`. If the link is repeatedly dropping, the cause could be the cable, router, network adapter driver, or the ISP’s DHCP service rather than CGNAT itself.

Your ISP cannot change your computer’s MAC address remotely. A changing public IP or DHCP lease can happen with CGNAT, but that is different from the local Ethernet adapter’s MAC address. Check whether the Ethernet interface still has a local IP when the problem occurs, and inspect NetworkManager’s connection and system logs. Avoid switching to a manually assigned address unless you know the correct IP, gateway, DNS servers, and subnet; an incorrect static configuration can make the connection fail.