2003 Land Rover Discovery P0130 Fault: Is It the Front Driver's Side O2 Sensor or Fuel Type?

I'm experiencing a P0130 diagnostic code on my 2003 Land Rover Discovery. I want to confirm whether this code specifically points to the front driver's side oxygen sensor. Some sources suggest that the type of fuel I use might be causing this issue—could that be accurate? Another theory I've heard is that it could relate to the catalytic converter, though I know that on fuel-injected vehicles like mine, converters typically last a long time. Since I'm trying to save money, should I only replace the single O2 sensor (sensor 1), or do I need to replace all four oxygen sensors? What troubleshooting steps can I take to confirm the root cause before replacing parts? Any reliable diagnostic advice would be greatly appreciated!