Hello,
NoMachine transfers the pressed key and injects it on the server at the system level. If we understand how Karabiner is working, doing the remapping of the pressed key to produce a different event, as it remaps the physical key, it should also remap the key injected by NoMachine. Since that’s not the case, it means that Karabiner works at a different level of the device handling stack and that the key NoMachine sends is interpreted by the OS by-passing the capture Karabiner does. Unfortunately we don’t know at which level Karabiner is working, so you should probably try to contact the Karabiner support.