Not sure how this works in the US, but I know a few people - notably, a couple whose been at this for a decades - who buy and stake claims on cheap Crown land around Canada. They'll travel in their 4WD Vandura from spot to spot, maybe stay for a few weeks, up to a year, in each spot. When I say cheap I mean in the hundreds of dollars to thousands, and hardly ever any more. They keep gardens or food forests on a few of the plots they'll visit more frequently. The nice thing about food forests is that they're self-sustaining, so you can be away from them for a while and they'll do fine; laborious to set up but resilient without human input after that.
The only caveats are that they have to produce some resources from the land if you intend to renew the claim - but within a 10 year window, so you've got lots of time to pan a bit of gold or cut cord of lumber. The other caveat isn't really one to people here... there's no infrastructure, no roads, so you've got to break trail to get to your staked claim. You could build a road if you want, heck, you could build a cabin or greenhouse (so long as they're on skids or could hypothetically be moved somehow), but it's not necessary.
I don't think they're on OB, but I'd be happy to get anyone who is curious, in contact with them.
As for indoor gardens in fulltimes rigs; there are plenty of folks in the skoolie communities who will grow potatoes in a box, grow microgreens, herbs, beans and peas even.