That's great. It's going to be much easier to install than I first assumed. All (I guess I should say most) of the typical house load neg wires, solar included, go to common buss bar that I installed when I did the major electrical upgrade a few years ago.
It looks like buss bar main wire, chassis ground & inverter neg on the other side of the shunt.
Trimetric, Samlex 1500W, some 2GA all to be installed ............. guess who's online garage sale I visited?