I’ve been trying to see how few thermometers I could use with global entropy to create a unique solution. Turns out the answer is one, the puzzle is just absurdly difficult. Enjoy!
Normal sudoku rules apply. Every 2x2 box must contain one digit from 1-3, one from 4-6, and one from 7-9. Digits along a thermometer must strictly increase from the bulb end.
Try it on CTC

Solution code: Row 4
Solved by SKORP17, jalebc, oiyad
Comments
today, 13:46 by Katuize
Entropy is by far my favorite constraint! Unfortunately I haven’t mastered the technique yet. I do see some play around R3/4 and C3/4 but I’m struggling to move forward without heavy bifurcation… any advice on next steps or tips?