As @amin noted in Dec 2021, NoMachine’s UI is tiny and not usable on a 4k screen.
@Tor responded: “We’re working on some changes for HiDPI displays, which will also introduce improvements to the general UI look.”
It appears such changes have not been introduced yet. With NoMachine’s popularity on Linux I’m surprised there isn’t more noise about this. I have a Java application that does the same thing, but learned that the execution script can be edited to scale the app directly. Has anyone found a workaround to make NoMachine legible on a 4k monitor?