If you can't get a 23 mm offset box wrench allowing to hold into the strut so that it doesn't rotate as well, a modified socket can do the trick.

1. Obtain a 23 mm (ideally) or a more common 15/16" deep socket.

2. Cut a 0.25" centered 1.25" above the socket base going around about 2/3 of the circumference. Use the socket points as guides. I used an angle grinder to make the cut.

3. Insert socket onto strut nut.

4. Fit 10mm wrench into slot onto strut flats. Make sure socket is positioned such that maximum relative motion can be attained before interfering with fixed 10mm wrench.