Hacker Specterdev has published an explanation of the 5.05 PS4 Jailbreak, which relies on flaws in the BPF driver, similar to what the 4.55 exploit did (except more complex because Sony strengthened access to BPF since the 4.55 exploit).
The article is extremely well detailed, but deals with a very complex topic, so don’t expect to understand much unless you’re very well versed in system architecture (it’s still an essential read if you expect one day to find your own exploit!).
It shows exploiting techniques have become very advanced, as a reply to the progress made on OS security by Sony and other console manufacturers. In particular, Specter describes how the System regularly checks whether the stack pointer is trying to run userland when it shouldn’t (that is, when it’s running in a kernel context), and how this made implementation of the exploit much more complex.
Of note, among the people credited in this writeup is TheFlow, and I believe this is the first time I’ve seen him being mentioned in the context of PS4 hacking.