Look up videos and channels dedicated to homesteading. I am truly impressed at how high tech harvesting has become. I know a great channel with a family that specialized in living off the grid, growing all their food for the entire year without outside help. There's an entire community of these people in basically every video sharing site, so once you find them there's dozens of them to learn and share ideas from.

The one I watch uses jarring to preserve crops as foods year-round. I know it technically isn't OFF the grid, but glammed up farming has many ways to produce foods including freezing. The space does add up in some form however, so I do agree with your assessment.