Since Ready or Not relies on official Steam servers for matchmaking, pirated versions almost never have working multiplayer. You will be locked out of the core cooperative experience.
(best gear for non-lethal vs. lethal runs) Ready or Not Free Download (Incl. Multiplayer) ...
If you'd like to dive into the or need a beginner's guide : Since Ready or Not relies on official Steam
Many sites claiming to offer free downloads bundle the game with spyware, ransomware, or miners that can steal your personal data or damage your hardware. Ready or Not Free Download (Incl. Multiplayer) ...