Finally:
View attachment 1701809
Had to boot the system disabling OpenCore normally needed to switch on the AMD video acceleration. First installed the latest 19H14 using @dosude1 patcher (install to disk) and applied directly the latest security update..
Now patching for iMac 2011 and sleep...
my personal iMac12,2 recipe starting:
1a. disable OpenCore
1b. disable SIP (has been before)
2. download and install
@jackluke OTASWfix app
3. start the app and follow the on screen instructions - OTA upgrades will be detected and downloaded into the /Library/Updates folder
4a. let the iMac reboot several times and install the upgrade until it is finally done, check the version, should now be 19H505, if not proceed to 4b
4b. if installation fails then delete contents of /Library/Updates and start over with 3.
5. reboot into the @dosdude installer (regardless which OS version) and run the post install patches option again
6. reboot into your Catalina 19H505 and let the patch updater install missing patches
7. reboot again and install iMac12,2 sleep patches
8. enable OpenCore again on next reboot
9. run test apps as Valley OpenGL benchmark to check basic functionality
Honestly, installing Big Sur is more easy than this....