Reading about the first Perimeter, I came across mentions that most of the backstory was cut in the English translation, and that there's loads of lore in something called "P-files". Can anyone tell me more about this, and perhaps point me towards where I might learn more about this?

P-files are a set of short sci-fi stories which were supplied on CDs of Russian release of the game (I don't know if they were translated with Codemaster's release of the game. Probably, not).

It's true, the English version does omit large parts of the story. Back in the day, I extracted the game's script and translated it to English. Unfortunately, I don't have the translation anymore. It has been lost.

P-files are an additional source of lore. I don't remember if they have ever been translated. It would have been pretty difficult.

Found the Russian text I extracted from the game's database: https://pste.eu/p/46Fh.html

The truth is out there.

Before the Pyramida mission there is a briefing on the history of the frames... I can only see the first 3 dialogues, and then there is no option to "continue". Strange and quite annoying.