Almost all mid-range smartphones today already come with the NFC chip, including devices from OnePlus.
NFC is a radio technology for near field communication.

Thanks to NFC, many processes can be completed via devices in the vicinity, such as paying with a smartphone by simply holding the device up to the terminal, or transferring data via Android Beam to a new or different smartphone.

In order to establish a connection via NFC, the devices do not have to be paired with each other, as is the case with Bluetooth, for example.
In this case, it is sufficient to be within range of the device to be received/transmitted.

Note: NFC can also be turned on/off at any time using the quick settings in the status bar.

Android 10 | OxygenOS 10.0
NFC -  Open the  Settings
NFC -  Tap on  Bluetooth & device connection
NFC -  Enable or disable  NFC
  1. Open the Settings
  2. Tap on Bluetooth & device connection
  3. Enable or disable NFC

OnePlus Instructions