Method A (Automatic): Power on the device. Many smart units automatically detect valid firmware on the USB drive and prompt you to update.
of the TV or device you are trying to update so I can help find the exact official support page? Insta360 link2pro Tutorial-Firmware Update ums5121h10natv firmware update link
Check the support section of the company that sold the unit (e.g., Eonon, Joying, generic AliExpress sellers). Method A (Automatic): Power on the device