In order to install NoMachine on Amazon Linux 2 OS, it's necessary to use the tar.gz packages.

Be sure to set firewall rules while creating the Amazon instance in order to open 4000 tcp and udp port, and port 4443 for web sessions (not available with NoMachine free). See section 'Configuring the security group' of this tutorial: https://www.nomachine.com/accessing-your-remote-linux-desktop-on-amazon-elastic-compute-cloud-via-NoMachine

You can find below the steps we followed in our labs. Run from a terminal:

$ sudo yum update
$ sudo amazon-linux-extras install mate-desktop1.x
$ sudo adduser testuser
$ sudo passwd testuser
$ wget https://www.nomachine.com/free/linux/64/tar -O nomachine_7.10.1_1_x86_64.tar.gz
$ sudo tar zxf nomachine_7.10.1_1_x86_64.tar.gz -C /usr/
$ sudo /usr/NX/nxserver --install redhat
$ sudo sed -i "s|^DefaultDesktopCommand.*|DefaultDesktopCommand mate-session|g" /usr/NX/etc/node.cfg

Instructions above set Mate as default desktop, you can change them to adopt a different desktop, preferably a lightweight one.