I was able to successfully enable the nxaudio module in macOS Catalina, and the microphone and audio adapter appear. However, I get no sound out of them when streaming from NoMachine to another device. I can see that the levels are moving while sound is playing, so NoMachine is picking up the sound, but it isn’t passing it to the other device.
Both nxaudio and the whole NoMachine application are added under Security and Privacy->Accessbility. The microphone is also enabled. I have tried the iOS, Ubuntu, and Windows clients and none of them will stream the sound.
The problem is caused by the bug in the macOS Catalina Beta. For now, it is impossible to stream audio from this operating system. However, if you want to use NoMachine as a Client and stream audio from other machines you can use workaround. Open terminal and type:
/Applications/NoMachine.app/Contents/MacOS/nxplayer and then establish connection to the desired machine. Audio should work properly.