Never use your primary Epic Games account credentials with third-party launchers. Most community projects use "dummy" logins or local profiles to prevent bans. Conclusion
Because Fortnite is a live-service game, the official Epic Games Launcher only allows users to play the current, live version. An offline installer for v13.40 serves several unique purposes: Fortnite Battle Royale Offline Installer - v13.40
Communities like "Project Rift" or "Era" use these specific builds to host private servers, allowing players to revisit old maps. Never use your primary Epic Games account credentials
Small communities hosting their own games using emulated backends. Risks and Safety Precautions Fortnite Battle Royale Offline Installer - v13.40