If you need something running fast and easy buy a synology nas. Not the best hardware and expensive geat if youi dont have the time to mess around with stuf like unraid etc. There a lots of great guides on setting op docker containers on that. https://drfrankenstein.co.uk/ is a geat example of easy to follow guides.

Amagettron advanced en soldat are fun games (not sure if they’re open source)

Look into open therm gateway with something like a dumb Honeywell Round modulating thermostat unless your thermostat already supports open therm.