OOOO, That is a nice unit there. That will be a good option for some.
My ghetto camper is already setup with cigarette lighter electrical, with ample extension cables and such available to borrow, so I'll still be going with the adapter I found.
At my work, I have gotten a number of UPS units, some quite nice, that are perfectly good after a battery swap. Most nowadays are black start capable. Running battery DC through an inverter, only to step it back down to DC, makes me cringe when I think about conversion losses. Buuuuuut, if you got it for free/low cost and are okay with carting it about, I'm sure we will see some people doing that too.
Hopefully other people, who have their own solutions, will chime in. Give people as many options as possible for their own particular needs.