Installed 11.1 (20C69) on MBP5,2, on external USB ssd.
Refrained from OTA installation once more, but used full installer obtained via MDS.
Prepared khronokernel's USB OpenCore Legacy Patcher 0.0.3 (page 1 option 4). **
Updated existing USB BS installer made with jackluke's BigSurFixes (page 1 option 3), using the BigSurSharedSupportfix.command with 11.1 installer app in /Applications.
Then using this installer in two ways. In both cases starting stage1 from USB BS installer.
- 1st way: continuing stage2 and stage3 from USB BS installers's Utilities pulldown menu, applying Legacy USB and graphics framebuffer fixes, omitting Frameworks fix (nightshift) this time. Booting via Apple boot selector.
- 2nd way: continuing by booting macOS installer (at start of stage2) via OC-L-P and not applying patches to disk. Booting via OC-L-P.
In both cases installed over 11.1 beta2. In both cases boots fine into setup of BS 11.1.
** In the OC case, I first tried version 0.0.7 but got an error message and reboot soon after starting stage2, related to SerialATAPI reconfiguration (picture). Tried again with 0.0.3 without problems.
Thanks to jackluke and khronokernel.