Unofficial, community-provided workaround. Not affiliated with or endorsed by Epic Games.
This PowerShell script addresses a narrow clean-install finalization failure: Unreal Engine 5.8.x has already downloaded, BuildPatch/BPS finished successfully, and the editor works when launched directly, but Epic Games Launcher displays Resume because it never committed the installation metadata.
It is based on one successful UE 5.8.3 recovery. The generalized version has not yet been tested on additional machines.