I went to sleep as Software Update downloaded so slowly this time, and set an alarm at 20:00 UTC. I had made sure my kexts are the latest, but I still encountered the infamous black screen. I used the boot arguement
temporarily and installed WhateverGreen 1.3.4 which is too new and not provided by Hackintool that I have been relying on for months.
Everything works now. All machines with a Radeon GPU should be installed with WhateverGreen 1.3.4 or newer to make sure you will not have that black screen from macOS 10.15.1 (19B88).