HestiaPi is the only purchasable open source thermostat that is mostly plug and play as far as my research has found. I'm looking to get rid of my Nest V1. I haven't had it on WIFI for 4 or 5 years because it wouldn't take my password after a version update around then. I did a hard reset after that and it is running its out if the box smart mode now.
My biggest concern with HestiaPi is that its GitHub looks stagnant. Does anyone have any experience with HestiaPi? Is it secure and stable? Are there any other projects that I'm missing out there? FWIW, I am not into home automation and don't want any solutions in that respect.