The preview is 'applied'' to the output of the Pi right at the end of video processing, its sort of 'superimposed' on the output. This means that things like remote desktops, which mirror the frame buffer, or ssh which is a text protocol, have no idea that the preview is even there.
VNC does have a mode that might help but consider this - the preview is a large image being refreshed at 30fps, which is a LOT of data. when viewing remotely all that data needs to be transfered over the remote link. So, I think VNC has a mode that compresses the data (H264?) before sending it to reduce the bandwidth requirements, but of course tha increases the encode and decode requirements.
So, its not a trivial thing to do.
You could try streaming the camera H264 output to your remote system and decoding there. There are posts about how to do that on here.
Principal Software Engineer at Raspberry Pi (Trading) Ltd.
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