Check what value the system settings of Ubuntu 24.04 ‘Scale option’ is set to. Change it to 100. We are aware of a problem with scaling on server side, which you can monitor using the following link:
Only a part of the desktop is rendered on 4k monitors scaled at 150%
https://kb.nomachine.com/TR11T10690
You could also try changing the view mode in the NoMachine Display panel to ‘Enable viewport mode’ or ‘Scale to window’. Alternatively, in the NoMachine menu panel open Display -> Change settings and try setting a custom resolution in ‘Use a custom resolution’ W/H).