If you need a "cleaner" offline installer or require custom modifications, downloading the source code from GitHub is the professional route.
Go to the EpicGames/UnrealEngine GitHub repo. Switch the branch to 4.27 . download full unreal engine 427 offline installer
Navigate to the "Library" tab, click the "+" sign, and select version 4.27.2. If you need a "cleaner" offline installer or
Click the green "Code" button and select Download ZIP . This is your "Source Offline Installer." click the "+" sign
Once downloaded, navigate to the installation directory (usually C:\Program Files\Epic Games\UE_4.27 ).
On your offline machine, paste the folder. To run the engine without the launcher, go to Engine\Binaries\Win64 and run UE4Editor.exe . Method 2: Building from Source (True Offline Setup)
Connect your Epic Games account to your GitHub account via the Unreal Engine website .