One day when I have some extra bucks I'd try to get a home server running, but the idea of having something eating grid electricity 24/7 doesn't seem to play along well with this 3rd world budget. Are there some foolproof and not so costly off-grid/solar setups to look at (like a Raspberry-based thingy or similar)?
Mac Mini (M1 and later) under Asahi Linux just uses 5 W for a normal workload. If you push it to 100% of CPU it reaches 20 W. That’s very little.
Only thing is you can't run Proxmox which makes self hosting much better, and you'll be limited to ARM builds, which on server is at least a lot easier than trying to run desktop apps. Modern micro desktops are also fairly power efficient, perhaps not quite as low as the mac, but much lower than a regular gaming desktop idling.
Avoid stacking in too many hard drives since each one uses almost as much power as the desktop does at idle.
I doubt anyone who is too tight on cash that they have to think about the electricity cost of a home server can afford a Mac.
Your fridge and other home appliances likely use much more power than whatever a small server would. The mini PC in the article is very power efficient. You likely won't notice it in your power bill, regardless of your budget. You could go with a solar-powered setup if you prefer, but IMO for this type of use case it would be overengineering.