Summary

Arduino nano clone, environmental sensor (I2C), relay (TTL), button (TTL), 4 digit alphanumeric display (I2C)

Smush it all together, throw some code at it, and you get a thermostat!

needs four 2.5mm by 20mm self tapping screws, and one 3mm by 15mm nut and bolt.

print at 102% scale. 10% infill was more than enough.

EC Buying 2Pcs 0.54" HT16K33 4 Bit Meter Digital Tube Module Emerald Green Color 0.54 inch LED Display Module I2C IIC for Arduino
https://www.amazon.com/dp/B0C1C6LKDB
AEDIKO 10pcs DC 5V Relay Module - 1 Channel Relay Switch Board with Optocoupler Isolation, High or Low Level Trigger
https://www.amazon.com/dp/B0BHLDW9G5
Diitao 7PCS AHT10 Digital Temperature and Humidity Sensor Module High Precision Measurement Modules 1.8-6.0V I2C Communication Replace DHT11 SHT20 AM2302
https://www.amazon.com/dp/B0BBLPTNF8
ELEGOO Nano Board CH 340/ATmega+328P Without USB Cable, Compatible with Arduino Nano V3.0 (Nano x 3 Without Cable)
https://www.amazon.com/dp/B0713XK923
100PCS Panel Mount 10mm Momentary OFF-(ON) Push Button Switch Upper Screw Thread
https://www.aliexpress.us/item/3256806216667200.html