Maybe you guys have already heard, a core portion of iPhone source codes(iBoot) was leaked. https://motherboard.vice.com/amp/en_us/article/a34g9j/iphone-source-code-iboot-ios-leak
Although Apple was able to take a DMCA removal action on GitHub, in some other repos it’s still active! Here’s one that I found: https://0xacab.org/sizeofcat/iBoot/
Might not stay long. (I’m merely sharing the repo, not responsible for uploading it or creating it)
Edit: The repo above is already gone. I believe most of the early members already have it.