Whenever I click or press any key on my keyboard, the game lags. I changed my settings from Unlimited FPS to 60 FPS if that helped and nothing worked. It makes it so I literally cannot start the campaign for Halo: Reach.
It does the same thing for me, as well as on Gears 5.
I’m lead to believe its an Easy Anti Cheat problem. When I load the non-AntiCheat version of the game, this problem doesn’t occur.
Are you using an RTX graphics card by any chance?
Please see the pinned thread regarding Halo Support and how to submit tickets for issues you may be experiencing.
Turns out razer is the real culprit. If you’ve got razer synapse or cortex, disable/uninstall them. It worked for me.