This will place you on a better path. Basically, you want the tar file versus rpm. The installer has no clues about Clear Linux. To remedy this, specify fedora so that the installer has an idea of what the system closely resembles.
NoMachine expects its files residing in /usr (e.g. /usr/NX). Therefore, the -C /usr argument is specified to the tar command.
Attempting to install to another location will cause the installer script to partially fail. Unable to install to another location is a regression on their side (e.g. NX_INSTALL_PREFIX=/opt). Something or awk may fail due to looking at /usr/NX. For that reason, I recommend installing to /usr.
# First, create the /etc/pam.d directory (important).
sudo mkdir -p /etc/pam.d
# Obtain and extract the nomachine tar file, from nomachine.com.
sudo tar xf nomachine_8.4.2_1_x86_64.tar.gz -C /usr
# Installation.
sudo /usr/NX/nxserver --install fedora
# Disable/enable VirtualGL.
sudo /etc/NX/nxserver --virtualgl no/yes
# Audio support.
sudo /usr/NX/scripts/setup/nxnode --audiosetup /usr/share/pulseaudio
# Printing support. Note: This does not work ???
sudo /usr/NX/scripts/setup/nxnode --printingsetup /usr/share/cups
# Start the service.
sudo systemctl start nxserver.service
# Check the status.
sudo systemctl status nxserver.service
If you want, possibly reach out to the NoMachine folks about Clear Linux resembling Fedora Linux (e.g. using systemd). Provide also the audiosetup path. Maybe more companies will support Clear Linux. It requires the first step, reaching out. I did so for RealVNC (VNC Server/Connect) and TurboVNC.
# To uninstall NoMachine (e.g. to start over if needed).
sudo /etc/NX/nxserver --uninstall
Unfortunately, sound doesn’t work for me. I tried various things to improve performance. I am sadden that you did not try TurboVNC.