Remove some other lug bolts to see if corrosion is an issue, if it is ,start soaking it with penetrating oil repeatedly.

Thoroughly protect the wheel with duct tape or the like and start grinding in the center of the the lug bolt.

Could try grinding a notch off center to put a punch into and then striking the punch in the loosening direction.

If a used wheel is available at a fair price you could sacrifice the wheel by grinding it away but that would be my last resort.

Change all of the locks, they have likely been subjected to impact tools.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer