Installing Monterey on Late 2012 27 inch iMac

[Late2012-abc]

Hi everyone,

First post on here. I hope someone else has done what I describe below and can advise re. my questions....

I have a late 2012 iMac (27 inch) which is currently running on the latest version of Catalina (10.15.7).
It's no longer getting updates and Office 365 updates can no longer be applied either.
I want to update to avoid any future issues , security etc.

About 6 months ago, I installed Catalina 10.15.7 on an external SSD and it was a game changer re. performance .

I am looking to do the following:

1) Buy another SSD and install Monterey on it (or Ventura, if it will work as well). Using Open Core patching.
2) Backup my current Catalina SSD (in case I mess things up )
2) Boot from the new drive , instead of my Catalina SSD.
3) When all is working, copy my data from the SSD and the original MAC hard drive to the new SSD (Monterey image).

I assume I will be able to use the Open Core patch process to do this (there are some good YouTube videos show how to do this and it doesnt look too complicated)?

Importantly, once I have done this, can anyone advise if Apple iOS updates get applied automatically, or will I have to do these manually going forwards?

A point to note: I currently have the original Catalina (10.15.7) iOS on the Imac (which has a standard Hard Disk - very slow).

 

[Late2012-abc]

I guess, to put it in simpler terms, is:

what is the best way to install a newer (still supported) version of Mac OS on a fresh external SSD drive which will ideally receive automatic updates in the future. Can the Open Core method be used to do this?

 

[DarkPremiumCho]

The OpenCore Legacy Patcher should work for you, but I suggest following their official guide instead of relying on YouTube videos.

You will receive macOS (not iOS) updates quite similar to those during the Catalina era. However, there are some caveats.

• Your iMac will have to download the entire macOS to update, even it's from 13.3.0 to 13.3.1.
• Some apps may not function properly due to the graphics driver being supported by community patches.
• You will need to run OpenCore Legacy Patcher again after every update.
• Security level is downgraded because System Integrity Protection will be disabled. There are debates on this topic.

 

[Late2012-abc]

Many thanks

The OpenCore Legacy Patcher should work for you, but I suggest following their official guide instead of relying on YouTube videos.

You will receive macOS (not iOS) updates quite similar to those during the Catalina era. However, there are some caveats.

• Your iMac will have to download the entire macOS to update, even it's from 13.3.0 to 13.3.1.
• Some apps may not function properly due to the graphics driver being supported by community patches.
• You will need to run OpenCore Legacy Patcher again after every update.
• Security level is downgraded because System Integrity Protection will be disabled. There are debates on this topic.

Many thanks for this. I have re-read the OpenCore Legacy instructions and all looks pretty straightforward. I will give it a go and install on a fresh SSD and see how it goes re updates / security etc. Nothing to lose except £20 for the new 480GB SSD, which I can swap in and out with the one I have Catalina on (enclosed in an enclosure). Thanks again.