This article completely glosses over what is presumably the first step of making this work, which is getting a shell on the Kindle. The only resource is some random forum bulletin board post? Huh?
I don't think phpBB threads ever change URL these days. It's only unreliable if the forum is managed by a video game company, because they delete the whole forum every now and then to renew their website. But MobileRead is well-known and enduring.
I suspect it's less that the forum will change URLs as that the URLs listed within some arbitrary forum post will become outdated as the referenced source moves or is deleted.
Linkrot, in other words.
Documentation in Wiki-based formats is more resilient against this as posts can be subsequently edited.
Why is the source-of-truth record for a set of complex technical instructions in a bulletin board board of all places? Instead of, you know, checked in as code in a version-controlled repository, like basically all other software?
Be the change you want to see in the world. In the time you spent complaining about it here you could have made such a resource. Don't ask the Internet in general to do it for you.
No, I could not have, because I don't own a Kindle nor do I have any way of exercising the instructions. I'm just calling out that this is an asinine delivery format.
Jailbreaks are highly firmware and hardware specific. I've only seen one specific combination (5.13.5, PW3), but the LanguageBreak authors have seen hundreds -- including mine -- so I have no additional insight or instructions that the extremely thorough LanguageBreak thread doesn't have.