Considering how open Tesla is with service manuals and even their in-car diagnostic menus, hopefully Rivian can catch up with them. https://service.tesla.com/en-US/
I highly doubt its liability with HV wanting them to keep it closed. Probably more they want everything to go through service...
There's a fireman/manual release cable for the frunk in front of the front driver wheel well. Keep a torx driver (T20 and T25) hidden (magnetically?) somewhere and a jump pack in the frunk and you should be able to bootstrap the 12v solo.
Also worth noting not to keep priceless valuables in the...