Programmer Connector #1

You will need an external programmer for the firmware flashing process.

@IsmaelHG programmer with which type of connector? Proprietary Apple's one?
Cause I've searched it recently on AliExpress and one connector with short cable costs more than 100$.

Originally posted by @th3sk4 in sicreative/VoltageShift#44 (comment)

If you have an 15" 2013-2015 MacBook Pro, you can flash with a SOP8 Clip which costs only $3.

On other MacBooks, you can use a JTAG adapter or desolder the BIOS chip and solder it into an WSON8 adapter.

Bad news is that the JTAG cable is expensive as you said, the cheapest option I found is this one in eBay for $60
https://www.ebay.com/itm/133187974519

I bought this exact same cable a year ago and it works fine.