Installing Inverter Chassis Ground location

Besides the positive terminal and negative screw connections for an inverter, where should the third chassis/ground go?

I got an EVExtend kit and the instructions say "If your inverter requires a safety/chassis ground connection, connect part as
shown on the negative battery post" (See picture, green wire). However I've seen a few posts on this forum that say not to connect to the negative terminal directly, and some that say this might just be for 2011-2012 leafs due to a sensor there. I have a 2015 leaf and am wondering if these are correct instructions for me - what would be the best place to connect to?

I also considered connecting to real ground or a house outlet ground outside of the car an the EVExtend maker said "Despite the nomenclature, there isn’t a need to connect this to the physical ground that the vehicle is resting on." Some of the forum posts seem to suggest this is also not the case, that a real ground would be best. Just want to check that the maker is correct for these cases since there is conflicting info.

There is supposedly a connection block under the dash that is used for the Bose stereo when present. You may want to try to find that. Otherwise just look for good, bare metal to bare metal grounding locations in the motor compartment. There is a smallish one on the PDM stack (the assembly that looks like a cylinder head with valve cover) on the upper right side (viewed from the front), facing the accessory battery. We use that for battery maintainer lead grounding.