We were boon docking at an archery shoot when the neighbor plopped a genny in the weeds behind us.
I was quite enough and he mentioned that since behind us was the only practical location we may as well plug into it. it was for daytime use only.
While the availability of electric was nice I am not sure it is worth the hassle to me.
In answer to your question, a log chain and lock are the best you are going to do. If the thieves want it and have time they will get it. Running it in the truck bed with a good exhaust fan seem practical also.