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.
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.
Bend the end of a zip tie into a U shape roughly the size of hole spacing and try feed it in one hole and out another.