Semi-related. I wonder why Mac OS does not provide any setting to keep the laptop running with the screen closed. You either need to use third party software or connect a dummy HDMI dongle. Both of which cost additional money for a function that is furnished as a matter of course by other operating systems.

There is a setting for it, it's just not exposed in the GUI.

sudo pmset -a disablesleep 1

As mentioned by the other commenter, `caffeinate -s` also works, but with the caveat that a) the command has to be running and b) the laptop has to be plugged in to power. Configuring disablesleep=1 completely prevents sleep and lasts until you manually configure it back to 0.

Thermal problem maybe ? The hot air escapes through the vent near screen.

You can use the caffeinate command (CLI) to do that, IIRC.