I must be doing something wrong here as after searching this forum and internet cannot find a solution.
Using a VNC client, and I’ve tried lots, the same issue. The mouse pointer and its actual focus is aligned when moving to the top left of the screen - as you move the mouse the divergence between the actual focus (you see this as icons are highlighted) and the actually mouse point grows, so the desktop becomes unusable.
I’m on MacOs and tired this on iPad and linux clients all the same.
The VNC in TrueNAS as in similar KVM based VM hosts connects not directly to a VNC server running in the guest OS but to an emulated “VGA” plus keyboard plus mouse console. Hence all the limitations.
With a remote access protocol connecting directly into the guest OS you gain
precise mouse control
correct keyboard mapping
copy & paste
sound to your local machine
mapping of folders from your local machine into the remote guest OS