Might turn into a Streetlamp Le Moose situation.
I bought one of those passively cooled router boxes from AliExpress and have been running opnsense for over a year on it now. It’s way overkill for router + ad blocking, but it’s been working great.
What’s the thermostat controlling? How is it wired up? I replaced mine with ram esphome with a temp sensor and a relay that bridges the pins when it wants to turn on. Mine is connected to home assistant but i think you can use esphome devices stand alone.
I did this for a while, but decided to just run opnsense on bare metal, I didn’t want my whole network going down if I had to restart Proxmox or something. It’s way overkill but it’s running opnsense, adguard and will soon be running ngnix hopefully.
The only reason I want it on the router is if either my vm or my server go down for whatever reason I have no access. My router is way overkill hardware wise (it’s running opnsense and Adblocking and I’ve never seen above 2%) cpu usage.
My zfs cache for 6x 4tb drives in raidz2 is about 10gb of ram.
I’ve used Hue Thief in the past. Usually works pretty well.