What are some methods of unlocking an Android phone?
Without getting into technical details, what are the typical methods of unlocking (using your device on another carrier), in particular Samsung Galaxy, Sony Xperia, etc.
I know of a few methods: carrier unlock, online unlocking with a code (requires payment to an unlocking site), rooting and installing a custom rom, and hardware add-on by connecting your device to a peripheral that assists in unlocking.
Many years ago, one could get free random unlocking phones for their dumb phone by simply entering their device's EMI and serial number. Is there another way that isn't mentioned where the consumer can unlock their Android device?