An update to the issue described in this topic:
Depending on the sound card on the Windows host, it might not be possible to mute audio on the NoMachine server side. If the Windows audio driver doesn’t provide functionalities like ‘mute control’, the WASAPI loopback capture can intercept only silence, when the server is muted.
Unfortunately there is no way to workaround this behaviour, but it’s possible to install and use the NoMachine Virtual Audio Adapter (NXVAC). On recent Windows versions like Windows 10 and 11, NoMachine installs only the Microphone Adapter, but it’s still possible to install the Audio Adapter manually.
More details here:
Muting audio on the server side on Windows 10 and 11
https://www.nomachine.com/AR04T01159