If the WiFi chip is fully broken, the console will show black screens with the blue LED on normally – but nothing else.
Not finding any access points? → Maybe the antenna cable is loose
O3DSXL or N3DSXL? → For the old model it is trivial to swap the WiFi board. Try another WiFi board if you think it is the problem. The WiFi is non-replaceable on new models.
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There is always my favorite method:
https://3ds.hacks.guide/ntrboot
Good luck and have fun!