For those who bricked their C20 v5 hardware
I did not know other C20 v5 variants even existed. My apologies. I'm here to help.
A TFTP firmware image is just an ordinary image with a bunch of zeros at the start. Anyone with a Linux machine can make one. I suggest you debrick your device by flashing it with a stock image via TFTP. I made a simple C program you can use to make stock TFTP images.
Refer to "How to Make TFTP Images w/ mktftpimg" here: https://github.com/ashegoulding/tp-link_c20-v5.dev
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Just out of curiosity, does it say "Model: Archer C20(EU) Ver: 5.0" on the label? Because mine does say "Model: Archer C20(US) Ver: 5.0". I don't see any reason why they would make any variant other than US. The difference is just regulations(power output). This is covered by the driver. Even if you do mess with the country setting(say, you set EU in US), it's not like the police are going to knock on your door with a warrant. Nobody cares!
If I were TP-Link dev, I'd just put different labels on the same model. Or maybe, flash the same hardware with slightly different fw(just the default country setting in rom partition).
Oh, I wonder.