Reproduction steps:

1. Open the Registry Editor ("RegEdit")
2. Go to "HKEY_CURRENT_USER\Software"
3. Delete "Unity" and "Unity Technologies"
4. Go to "C:\Users\user\AppData\Local\Unity" and delete/move everything
5. Go to "C:\ProgramData\Unity" and delete/move everything except ".ulf" files
6. Disconnect from the internet
7. Launch the Editor

Expected Result: The Launcher loads and lets you create/load a project
Actual Result: The Launcher is stuck on "Loading..." with no way to proceed

Reproduced with: 2018.3.0a2, 2018.2.0b9, 2018.1.5f1, 2017.4.6f1, 2017.3.2f1, 2017.2.3p1, 2017.1.4p2

Note:
Need to delete the Registry files between every launch of the Editor to repro