I’ve had a Pixel 4a for ~3 years at this point. I had to replace it some time last year because I had lost my original in a lake. T-Mobile gave me whichever lower-end Pixel there was at the time and I immediately gave it back because of the offputting amount of warmth it produced doing very little. When the time does come to properly upgrade, how would I go about searching for phones that run cool? I’ve been thinking about my next choice to be a jump-ship from the Pixel series given my, uh, experience (there was a bit more that I didn’t like about it)
Check for the chipset used on the phone. Usually phones that only uses ARM Cortex A55 cores never got hot and have longer battery life. They are usually pretty slow though. On the other hand, phones that have one or more ARM Cortex A7x cores (A75, A77, etc) in addition to A55 cores typically run hotter but run apps faster, especially when the A7X cores are configured to run at high clock rate (>2.5ghz).
For comparison, your old pixel 4a has 2 cortex A76 (2.2ghz) and 6 Cortex A55 cores, so I imagine it doesn’t run very hot. Generally, the lower the clock rate and the fewer A7X cores a phone use, the cooler it is.
There’s also the manufacturer to consider, the SD8gen1 and SD8gen1+ are basically the same chip, but made in samsung and tsmc fabs respectively. The tsmc made chip runs A LOT more efficiently.