I hear the echo only when using the microphone on NoMachine after starting the VoIP session. It echoes in Discord, Skype and the Windows microphone setup.
On my remote server I am using Microsoft Server 2016 and my local machine uses Windows 10. My headphones are my output device on my local machine, and I set NoMachine to disable sound on the server while streaming it back to me directly.
The default IO on my local machine is my USB headset, while the default IO on the server are NoMachine’s microphone redirection and speakers.
I checked whether the server or local machine is listening to the microphone and recording it, and neither of them were.