Sounds good. Maybe some sort of forum system, like https://github.com/hometown-fork/hometown (activitypub-based) or https://karrot.world or even an instance of lemmy ? Nextcloud is good as it has a lot of plugins for sharing photos and chatting etc. Video conferencing It would be worth looking at something like https://www.freedombox.org/ as it’s all self-contained, and might be easier to set up. at least as a proof of concept?

True, but it still seems rather excessive…

Yes. There are a few other chat clients that you can run relays for - Tox, SimpleX, Jabber/XMPP etc, which are worth investigating.

I like camping and festivals, and it was fun to get a small solar panel to charge my phone etc. about a decade ago. My parents were in to gardening, and used a lot of water butts to store water at our house. My other half and I watched a lot of Doomsday Prepper episodes (https://en.wikipedia.org/wiki/Doomsday_Preppers) during Covid lockdowns, and while some of them were a bit crazy, others had really good ideas. It felt like a sensible idea to try and be a bit more self-sufficient.

It will all take a long time to pay for itself, but I am learning about DC circuits and it feels good to have a backup for everything, even though we live in a city and are grid-connected to water, electricity and gas.

Still, it would be nice to see. Nothing wrong with second hand hardware - most of my setup is second hand. Here is a rather rubbish diagram and short explanation of how it is set up: https://mammut.gogreenit.net/@chewie/113075530030174991