my plan to fix the issue.
Setup 1: GA P55A-UD4 + HD5770 already running on Yosemite:
1) download High sierra, use Unibeast 8.4, select legacy bios, install high sierra on a dedicated SSD
2) running High sierra, download Catalina, run Unibeast 10.1, select uefi bios
3) upgrade hardware to setup...