Need another mechanic tip: lower ball joint studs turning with nuts?

If you talking about the ball joint (LBJ), I always put a jack under the ball joint and put enough pressure on the tapered stud (from the bottom) to cause it to jam in the "spindle" taper. Then you can usually turn the nut with no problem. Sometimes you have to put a lot of weight on the jack but eventually the tapered stud will get stuck in the spindle taper.

But your pic has red arrows pointing to the arm that's attached to the spindle???
treblig