Taming electricity usage without the cloud (zigbee / Sonoff)?

Hi folks. Newbie to the forum here but I am a techie who’s done a bunch of tinkering through the years.

Quick question for the group here…
I have a few rooms with a large number of high hats and Decor switches. While I’ve already gone LED I think that these guys are still consuming quite a bit of energy (especially since everyone has been home all day b/c of Covid).

I’d like a cheap way to default the switches to off during daylight hours but allow for manaul override. More importantly, I’d like NOT to be dependant on a mobile app that syncs to a cloud enabled service to get things done.

I can use an existing PC here or a R Pi as a server if need be.

What are your recommendations?
Can I fit a Sonoff module into the existing switches somehow (most are standard 2 way and not 3 way)? Should I go zigbee with a hub of sorts?

Any suggestions on cheaper solutions? I have more rooms than you’d think.

Thanks.

Welcome Newbie

I would go down the Shelly 2.5 Path

Sonoff mini and Shelly 1 fit nicely behind existing switches. And the can be used 3 way (or n-way) if wired correct. I have some shelly 1’s that can be switched by 3 switches (4 way ? )

Thanks. Sonoff seems the cheaper option (esp in larger quantities). I’m unsure if one has more features than the others.

I would also like to find some switches that track power consumption (these don’t need to be embedded in the plug or even trigger on/off function). I have a number of freezers I’d like to track consumption on. I also assume this will need more industrial 15/20A units.