On most Android phones, this opens Recovery Mode. However, on the OPPO F11, this combination typically leads to Recovery Mode , not Fastboot. From there, you can navigate to "Fastboot" via the on-screen menu (if available). If your F11 goes straight to a Chinese or English recovery menu, use the volume keys to scroll to "Fastboot" and press Power to select it.
Many users report failure. Here is why:
(and its variant, the F11 Pro) primarily utilizes a Recovery Mode How to Open Fastboot Mode on OPPO F11