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I am sorry but, as Privateer never had this option, neither does our version. Also DOSbox did not introduce inverting so far.

Still we have found a workaround for you - the only trouble with this is that it will invert your mouse in the whole game so I suggest using yout keyboard at stations and planets.

Just extract the files to Privateer's folder (so that the .conf file is replaced) and you're good to go.