Consider basing the essential infrastructure of the community on technology from around 1890. That allows gravity-fed water, wells and hand pumps, wood and masonry construction, passive heating/cooling, root cellars, canning and fermentation, animal and human power, belt-driven machinery, blacksmithing, woodworking, mechanical workshops, sewing, bicycles, railways, windmills, simple electrical generation, and sophisticated agriculture.
Base it on systems that people can understand, maintain, repair, and reproduce locally.
Then layer modern technology on top wherever it helps. Solar panels, electronics, automation, power tools, computers, modern materials—all wonderful. But when possible, let their failure result in inconvenience or more human labor rather than failure of the essential system.
If an irrigation controller fails, open a valve by hand. If a pump fails, perhaps gravity still moves some water. If refrigeration fails, some of the food supply still stores by other means.
Plan for graceful degradation: modern technology makes the community easier to operate, rather than making the community possible to operate.