Go with Qgis, there a loads of well written tutorials for using it and even step by step guids to do what you want: Example.
You can take ot a step further and host your maps online with either qgis2web like This, by using the build in tools or geoserver. You might even take it to the real world with qfield or an ar tool.
It's not i've bought two of them years ago because they have a decent spec rugged phone. The s60 was bulletproof and lasted ages and even a drop from standing height on concrete. I upgraded to a later model (i think s90) and that was a piece of shit. The quality control is crap, don't expect software updates but if you get a good one the hardware is great. So not a scam but i would stay away.
Streaming quality is horrible compared to bluray and a lot of movies never make it to the streaming platforms. DVD's are terrible but I some movies never made it to bluray of streaming.
That's where occupancy sensors shine. I generally don't have to touch my phone or switches.
Look in to BMBF, lots of songs that can be sideloaded on the quest.
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.
Try tailscale for remote acess run it as a docker container. I csnt help you with the other questions.