I’m also experiencing this issue. Space works for me, but arrows and all non-character input keys don’t work. I’m on an iPad 10 with a Logitech Combo Touch (pretty much a clone of the apple keyboard, so there shouldn’t be any difference software side)
My guess at why these issues are happening would probably be because NoMachine isn’t just taking direct keyboard inputs and forwarding them, but instead it’s trying to bring up the on screen keyboard and then that’s turning into the text input mode for a physical keyboard (it even shows the autocorrect/password bar). I’m kind of disappointed that the keyboard support isn’t better in the latest version, but hopefully that can be remedied with a future update.