I have a One Plus 7 Pro and it can scan QR codes, but you have to press a button in the camera app first. Not entirely intuitive up-front and a bit finnicky even once you know about it, but it's been good enough in practice.
I have the OnePlus 10 Pro. I've looked through all of the menus and settings, there's nothing that seems to be QR code related? Maybe they've removed the feature?
"oneplus 10 pro qr": https://www.google.com/search?q=OnePlus+10+Pro+qr
In 30 seconds, I found that you can do it by using the Google Lens feature, which is a button to the left of your zoom button in your camera app. If you don't want to use that, you can use google lens directly.