I understand you're looking for a full offline installer for Unreal Engine 4.27 (the last release in the UE4 series). Here’s the official guide.

Educational Institutions: Schools can request access by submitting an official offline request form. 2. Individual & Community Users

Is there an offline version of Unreal Engine for schools? - Gameplan

Options to obtain 4.27 for offline installation

1. Official (recommended): Epic Games Launcher — download engine components on an internet-connected machine, then copy the engine folder and cached installer files to offline machines.
2. Unreal Engine GitHub source: Build from source by cloning the 4.27 repository from the Unreal Engine GitHub (requires Epic account linked to GitHub). This lets you compile the full engine locally and move the built binaries for offline use.
3. Community packages or third-party torrents: Not recommended — may be outdated or unsafe and can violate licensing.

Disclaimer: This article is for educational and informational purposes. Always adhere to Epic Games' Unreal Engine EULA. All trademarks are property of their respective owners.

Epic Games allows redistribution of the engine only under specific license conditions (e.g., for custom game launchers). General-purpose offline installers are not permitted without explicit permission.

Or, for the EXE installer: