Hi!
I had the same issue and successfully fixed the my phone! On the pinephone discord I posted some images and will likely blog this down on my ballmerpeak devblog when I have the time for it.
You should get a prier/pry tool as it is very hard to open the keyboard with a guitar pick as I did it. The plastic to open go all the way around the hinge area where my trick was to slightly push towards it when it was elsewhere all opened. I also used a little knife but that does some outside damage so pry tool is better.
I can tell that the cables were torn both sides for me, but thankfully the cables are long enough in the inside so that you can cut the torn part and it will still be long enough without needing to add new cable part to it in my experience! I soldered it right to the end so it should be as new. The other side I cannot do this as cable was not long enough but for me was barely broken - there I soldered right where the hinge is - after removal of the bad part - then I applied a lot of duct-tape...
People on discord told me I should buy crimper tool to make a connector as when you pull it apart you will see there is a little pcb behind the pogo pin thing (that I also totally pulled apart and documented all steps with pictures just need to upload to my computer). There is a connector both on that (I think 6 wires go into a 8 wire wide or 8 wire into a 10 wire wide connector on backpanel side and two separate connectors for the two hinge-going cables on the keyboard side). So you can literally exchange cable. People in discord even told me probably you can order just a cable from pine if you ask cute enough but I went and soldered mine.... works fine still and extra strenght from duct tape I hope last for long.
Anyways. I came here only to see if this is where i discussed or not to look for what crimping tool I need as I might just buy one such jst cable crimper when already on aliexpress and just stumbled upon your question - but currently discord has all the best answers with some of my images that I posted.
So a successful repair was totally possible - and I am pretty much a noob / amatour for electronics as very tiny hobby so you should be able to pull that off too!
EDIT:
https://discord.com/channels/46323792798...9068554371
^^this link should work to see my first message and then keep scrolling downwards for other of my messages to see pictures of the process. If this is gone from discord anyway one time when a future reader reads this, I am pretty sure it will be on ballmerpeak devblog (that you can google up) on my blog - currently I was too lazy to upload the process of fixing there.
How to disassemble Keyboard top and replace cables?
