Other methods to unbrick LG X210 from other identical phone?
https://www.youtube.com/watch?v=A3TmXtOA0IA is this help maybe ?
my phone did react only to show the battery but after you plugin it ask for a signal 1 or 2 second only.you cant see it but you can prove it with usbdeview-x64.zip for example.then you need SP_Flash_Tool_v5.1804_Win.zip and the mtk usb drivers.
It was dead but i got it back to work.the links in the youtube video may be outdated but the information was very helpful for me , i did try to flash a custom twrp! but it wasnt for this device and kill the preloader too.

EDIT in the first two second you have to send the correct signal to hold it in 
the usb contact.

Edit MT6580 i-mobile i-style 712 is the device i  got back