How to uninstall Nomachine
As it says in the instructions:
sudo dpkg -r nomachine
See here.
The uninstall instructions are on NoMachine web (https://www.nomachine.com/DT02O00124#2.4):
UNINSTALL
sudo /usr/NX/scripts/setup/nxserver --uninstallthen, remove the installation dir:
sudo rm -rf /usr/NX