Interesting!
I could only find limited info about the SoC's TjMax / operating temperatures, although we could assume it's somewhat similar to the actual Tegra X1, in which case:
- This datasheet lists a TjMax of 105°C (page 2) and several thresholds before that (page 17) at which the APU would downclock (or shut down), with no actual value unfortunately.
- Gamers Nexus talks about the above, with a supposed throttling threshold at 70°C - and possibly 90°C - where frequency drops by 6%.
- Digital Foundry made a video testing Switch overclocking years ago (apologies for the ResetEra link, but there's a good summary there), where they had operating temperatures in the 60s (though I'm not sure that's the junction temperature).
That being said, my (V1) Switch is modded so I could test that a bit more, and check operating temperatures and frequencies before/after a repaste.
Excerpt from the dev's website (very bottom of the page):