Personally speaking, I’d suggest you look at a headless Linux based solution, maybe using something like the ODroid C2 machine.
Installing openHAB2 with apt-get couldn’t be any easier.
There is openhabian if you want an automated installation for 32 bit machines.
As for cloudless voice control, you might want to look at Snips.ai, with Snips clients running on tiny SBCs in each room, meaning that you don’t need to worry about presence detection to switch microphones, as the Snips Satellite units will only be monitoring one zone.
Or there is Mycroft AI if you can tolerate a cloud connected assistant that doesn’t share you data. (You can buy ready built units, or run their software on your hardware.)
I hope this helps.