I’m a total newbie when comes to cellphone repair, but the fix presented here worked like a charm and is relatively easy if you know how to solder. I’ve came across the solution on the iRepair channel on YT and below I post some photos from a microscope with a super brief explanation which the video lacks. First disassemble the phone and take a look at the “reference” image below.

No back cover reference image

The part that has failed in my case was the wide flat cable connecting the main board (PCB on the left) with the connector board visible on the right. Probably replacing the cable itself would work, but only if the sockets the cable is attached to are OK and we do not know that. In particular the line that fails is the positive voltage one, which (if I’m not mistaken) is directly connected to the USB-C socket VBUS pins. The Vdd connection is realized through the wide pin on the side of the FFC socket. Depicted below is how it looks on the main board side:

Power connection on the main board

Scrape off the solder mask and solder a jumper wire:

Soldered a jumper wire

Then do the same on the “connector board” (the one with the USB-C on it). I didn’t make better photos, to try to find the spot basing on the shape of the PCB and its traces. “connector board” prepared for soldering:

prepared for soldering

And here the same shot taken after soldering the wire:

Soldered the wire

And that’s it! Reconnect the FFC:

FFC on its place

And voila! It works:

Works

I’m definitely buying a new phone soon as this one caused so much trouble, but fixing it was fun nonetheless :D