I'm kind of in awe at how badly you messed up that connector. It's supposed to be a ZIF (zero insertion force) connector. At no point should you be physically pulling or pushing at the connector. Just flip up the latch (or sometimes there is a piece that you have to push out with a small tool, that takes more effort but still should not require force, I think those particular 2 are of the flip up kind though), gently pull the ribbon out, gently push it all the way in, and flip the latch back down. What did you do to rip it clean off the board like that? Did you forget to flip up the latch or something?
When I opened up my left JoyCon to do the foam connectivity fix, I was super worried about damaging the ribbon cables knowing they are fragile, but that was never an issue. Instead, I damaged the battery connector on the board, not knowing it came apart in two halves, I thought it just pushed onto pins from the side so I pulled at it and pulled both plastic pieces off the pins, one of the pins then broke and I scoured eBay for months for a faulty left JoyCon with good board for a good price with international shipping, and eventually found one with a faulty stick click from Germany for like €15 including shipping which I bought, since I didn't feel comfortable soldering the battery directly to the board.
But with ribbon cables, there are pretty much only a couple of ways the cable can latch in place, the latch itself can sometimes be damaged easily, but ripping the entire connector off the board? I've never seen that. I honestly wonder what you did to cause that.
