I am working on a residential 1 acre with an in-ground swimming pool with adjacent hot tub and patio perimeter. All functions, are working and/or operating, which appears wasteful for a pool hardly used. There are a few buildings, gardens, and chickens so far, and the property receives sun all day all year. The owner may be open to repurpose with convincing alternatives.
The easiest idea is rainwater storage, though it is always holding water. Aquaponics has been addressed, especially with core elements in place, but may be ambitious for now. I am also considering greenhouse options.
This image gives a general overview of the workings of a garden pool:
The only thing that isn't free with them is the most crucial part, a the complete guide to making a garden pool system. However, with the pieces the freebies they show online and the diagram above, I think a garden pool system could be pieced together without buying the guide.