Smooth update, eventually they’ve fixed 90° displays bug.
1. Updated Clover 4910 → 5070, it broke everything (pretty often situation, not surprised). Found out there are breaking changes, so I moved all my *.efi files from drivers64UEFI directory to the new DRIVERS/UEFI directory. (See attached images below.) It didn't help, then I deleted the original directories (drivers64 and drivers64UEFI) and it worked.
2. Updated macOS 10.14.4 → 10.14.6 through Settings, it went smoothly. I left the computer for an hour, and when I came back it was all done. I have no idea how long it took and how many reboot attempts it did.