I’ve seen this one which may fit what you’re looking for. No idea about open source firmware though.
This one might work for you too.
Really though, if you’re already spending money on a smart switch, you should probably just replace the outlet, other switch, and faceplate with decora (rectangle style) versions while you’re at it. It’s only going to run about $10 total for all those. Plus you can then use a smart switch that meets your firmware needs.
No, that’s normal and how it should operate. The problem arises when everyone is using the same software suite so everyone has immediate access to current prices, and the software essentially tells you what you should price your units at to maximize your income.
Maybe cartel was the wrong word as it wasn’t an intentional agreement between companies, just an outcome of the system and accelerated by instant access to information. A runaway feedback loop may be more appropriate.
I work in this industry. The biggest problem with the software is it gave the management companies instant access to everyone else’s current prices. The industry has used “market surveys” for years but you had to actually call around and gather those prices yourself. It’s a very time consuming process so many only did their surveys sporadically.
With the software you had instant access to current price data and everyone pretty much raised their prices to match the market average. Then the newer/fancier properties saw the new higher average and thought “We’re a better property so we can raise our prices above the competition.” Which then led to a higher average that the rest then met again. Rinse and repeat and you have a de facto price fixing cartel.
I have never felt so personally called out. I love it. 
Oh shit, I think I’m gonna be fine.