You need a pc with usb 2.0!
To un-root & Lock the bootloader, Qualcom driver it's NOT the most important thing!
No Qualcom 9008 driver in Device Manager.(win.10 pro_x64 with the latest updates). I tried to update, both auto & manual. Not working.
For Locking the bootloader i tried first Tool from Mauronofrio, then with ADB (drivers, adb/fastboot installed). Still does not see the phone in Fastboot/bootloader mode. With the phone ON, yes.
In MSM app Android 11 shows " Not connected". I read online that could be some problems with android 11.
I downloaded MSM Android 10 , now it shows "Connected", but does not show OnePlus or anything else. I said what the hell, press Start.
It worked. Nowi am Locked, no root on Android 10.
I plugged in OTG flash drive. Copy Oos 11.0.77 to root of the storage. Flashed.
Now i am on Android 11.0.77 Locked, no root. Ready to sell the phone.
My phone is european version. In MSM i selected EU, of course.