macOS Big Sur on unsupported Mac

Updated 2022-03-03 !

I'm having an old MacBook Air 4.2, (mid 2011, SSD, 4 Gb memory), which have been running Catalina for quite some time despite that the max OS is High Sierra. I have been using the great work by dosedudes1 and his Catalina patcher.

Unfortunately he didn't continue with patches for newer OS:s but have helped with a new patcher. This patcher even handles Macs with graphic cards from 2008 - 2011.

Using the patcher i got the mentioned Mac up and running with Big Sur after just over an hour.

 

New post !! Upgrade to Monterey.

Patcher manual

The manual for the OpenCore Legacy Patcher(OLCP) is nice and there are also a video that will help you for the whole process.

A recent video how to upgrade/use the OLCP to version 4.3 using the new GUI

Create bootable USB

You can create installers, for the most recent OS, via OLCP.

Another way is checking this post which will give more to choose from.

Building/installing the patcher

After that follow these instructions, on how to install and use the OpenCore Legacy patcher.

Good luck !

Remarks

• Erase/format the MAC HD/SSD before installation !! I really think that this does it more simple for the installer !! 
• With an old non SSD HD use "Mac OS Extended(journaled)" 
• With en SSD use "APFS"
• The Mac rebooted several times during install.
• Don't eject/remove the USB until at the very end.
• If you, like me, have a Mac which need the legacy video acceleration support please note that the Mac have a painfully slow display update before you have applied the "Post-Install volume Patch".
• Updating the Mac from Big Sur 11.4 to 11.5, made the messages.app stop working fixed in release 0.2.4
• Please note that a "Nightly TUI Build" are available, but just for testing purposes !!! Use the latest release instead. 
• In TUI "5. Miscellaneous Settings => 1. Set Showpicker Mode:" was set to "False"