How do I report a user for letting time run out?

Happened a couple times lately where my opponent left the game and all their remaining time run out. Not happy and I want to report them. I don't see the option from the game menu or from within their profile.

thanks,

The system detects this behavior automatically

I noticed the auto-warning. So does your answer imply that it's not possible to report other users?

The point is that it's automatically reported, so you don't need to do it manually.

If you really must vent about it somewhere, use lichess.org/report.

Бееее...

Thanks Thibault. I will not submit a report in this case, but it's nice to know where it is! thank you

As always stated that behavior gets automatically reported by the system. Though there is actually a button you can use to directly report the player to mods and that can be found in the player's profile on top right: the symbol with an exclamation mark inside a triangle. If you click on it, it addresses you to a page where you get asked which kind of issue you want to report them for and then to briefly explain the situation.
Always remember to send the link of the game!