If I am correct about what is going on, then there is a problem with mobile set-ups because the system may or may not be on shore power.
If the You-tube video is correct and it is OK to connect Neutral-in and Neutral-out, then this may be a solution for a mobile set-up.
View attachment 72509
With this arrangement, if there is no shore power, the relay creates the N-G bond. When there is shore power the bond is broken and neutral is connected to shore power. Notice that there can never be a time when there is both a shore power bond and the local bond.
WARNING: I have not built and tested the above circuit....