I can provide target troubleshooting steps or direct file structure directions! Share public link
[Base Game Folder v1.634.818.0] + [Differential Patch / Overwrite Update v1.642.644.0] = [Upgraded Game Root Directory]
While the exact steps vary by platform, the FH5UpdateV1.634.818.0ToV1.642.644.0WithDL concept suggests a manual installation process for players on older builds.