[Laptop] - Bad performance when connected to an external monitor, why?

[Airwave]

1) THE PROBLEM:
Hi to everyone, i am playing this game on a gaming laptop, Asus Rog strix scar 18 G834JY-N6048W. My problem is that whenever i connect my laptop to an external monitor (a Qled tv), via HDMI i get very bad performance without an apparent reason. Using the internal benchmark i get almost half the frame rate vs playing on the embedded monitor, using the same settings, and resoluition. I strongly suspect that the culript is the game, primarily because i routinely use this television connected to the laptop to play games, and so far no game i tried exhibited this behaviour. I ALWAYS get the exact same performance using the external or internal monitor (when using the same settings and resolution), I know this for certain because this is a test that i have always done since i have this laptop on every game.

2) A POTENTIAL LEAD?:
From my research it seems that this game has given owners of multi monitor setups a lot of trouble, and i wonder if my issue could be somehow connected to the inability of this game to properly detect the right monitor being used (even on desktop setups). This suspect is reinforced by the fact that when connected to the tv, the game let me choose refresh frequencies that my tv does not support, but the internal monitor of the laptop does. For Example at 3840x2160, the game menu let me choose frequencies up to 120hz which (coincidence!) is the maximum frequency of the embedded monitor of the laptop.
another strange thing is that i cannot change the active monitor from the settings menu, because it is greyed out (As only one monitor is being connected).

I sincerely thank anyone that could help me. And i remain ready to supply all further informations that could help in solving this issue.

[Armor]

I have the exact same issue. Looking for a solution online. Have you managed to find a solution for this? I get much lower fps on the external monitor also.