Ironwood 885, Char-Griller Flat Iron Premium griddle, InkBird Sous Vide
I drilled a hole in the front of the lid of my Ironwood near the center. I placed it so the tip of the temperature gauge would be about 1/2" above the top grate, but not touching. If it touches you get bad readings.
Here is the thermometer I used. It has a large 3 3/16" dial that can be seen from 20 ft away. It has a 2 7/8" stem that allows it to reach into the cooking chamber.
I recently purchased a Thermopro Temp Spike wireless thermometer. I am getting good agreement between the ambient reading of the wireless probe and the analog thermometer.
I do not have your particular Traeger model, so I cannot recommend a specific place on your lid to drill. Just remember to measure twice and drill once.