"Do you have a solution for a stripped truss rod nut?"

At first no, then the idea of a pin chuck surfaced. A pin chuck is used by pen turners that want to be able to turn a tube without a tailstock. A mandrel that is slightly smaller than the diameter of the tube and long enough to go into the tube and chuck, is used.

A flat spot is filed or ground on the side, the length and diameter  of the pin. ( I used a transfer punch and a finishing nail with the head cut off for my first pin chuck) When it's inserted into the tube the pin goes to one side or the other and jams in place.

A stripped 4mm truss rod nut was found. A one inch piece of .017 guitar string was inserted along one of  the flat sides of a hex wrench. It jammed just like a pin chuck allowing the wrench to both tighten and loosen.