I reinstalled the PC with Fedora 25 as more important to the user is to be able to access it remotely than to have the latest & greatest. NoMachine (7.1.3) is working fine on that version. I don’t have the time to see where NoMachine stops working on the various Fedora versions between 26 & 33.
I just tried this on a new server running the latest version of RedHat (Red Hat Enterprise Linux release 8.3) & the same issue appears. An older version of NoMachine is working normally on some older versions of RedHat with the same setup.
Not working – NoMachine-7.4.1-1.x86_64 on RHEL 8.3