Hello, I remember the topic with the first Surface devices. It was really annoying and simply unpleasant during prolonged use.
This is not the case at all with the Tab S9 Ultra.
The device doesn't get warm or even uncomfortable to use, even after prolonged use, whether for office applications, media consumption or other tasks.

We have been using the Tab S9 Ultra for over 3 months now. We also play a lot of online games on it. The screen always stays cool. Tested it again yesterday after hours of gaming. No noticeable heat, just room temperature.

I hardly ever use the PEN. I haven't noticed any heat. I use it a lot in PC modes with a keyboard.