I've been looking at ways to add a thermometer to the group head of a lever machine.
At this stage the options seem to be either:

Temperature Strip. Simple, cheap, responsive, fairly discrete, inaccurate. (e.g. https://flairespresso.com/product/temperature-strips/)
Digital Probe. Fairly cheap, responsive, accurate, ugly. Super ugly.

I was wondering if anyone had tried a digital probe with an analogue display? The only one I can find that looks suitable is an AutoMeter water temperature gauge: https://www.autometer.com/water-temp-pr ... -male.html

I've had good luck with a small infrared thermometer. I attached a clear circular sticker to the group head to take the reading from. (Chrome will not give an accurate reading because it is too reflective.) The look is good, the reading is quick - but does require an extra step to take the reading rather than a quick glance at something that's already installed. Absolute accuracy is not as important as consistency. Once you have an idea of what range(s) tastes good for a certain coffee(s) then you're good to go.

I should add that there's a lot of good ideas in this forum if you do a search.
Here is one of post that's helpful: Adding Thermometry to a La Pavoni Europiccola