To uninstall a system update on your OnePlus device, you'll need to follow these steps:
1. Go to "Settings" on your OnePlus device and select "System."
2. Tap on "System updates" and select "Storage usage" from the menu.
3. Find the system update you want to uninstall and tap on it.
4. Select "Uninstall" from the bottom right corner of the screen and confirm your selection.
Keep in mind that uninstalling a system update may cause stability issues with your device, so it's recommended that you only do so if absolutely necessary. It's also important to note that this process may vary slightly depending on the model of your OnePlus device and the version of the operating system you're running.