The shift from Proto-Indo-European voiceless stops like /p/ (or more broadly PIE unvoiced stops including labiovelars like kʷ undergoing specific developments) to Proto-Germanic fricatives such as /f/ is a well-established tenet of historical linguistics known as Grimm's Law, supported by standard linguistic literature.
The retrieved papers by Ringe (0), the discussion of Grimm's Law regarding /p/ and /f/ (1), and the comparative analysis of Grimm's Law from PIE to Germanic (4) all consistently support the historical linguistic consensus regarding Grimm's Law sound shifts, with no contradictory papers present.