Instructions for clean installation of OS Sequoia

Bob_GSO wrote:

I would like to perform a clean installation of Mac OS Sequoia on my 2020 M1 Mac mini. By Clean install I mean the following

Back up using Time Machine and jump drives for key files

reformat the drive while installing Mac OS sequoia to bring it to a T zero state

add personal files back via Time Machine.

My motivation here is there are new versions of several software packages I would like to install. My preference is to install these on a blank or virgin system to avoid any conflicts / messy references to the old versions of software. (open source software, freeCAD, KiCAD, Inkscape, Blender etc)

Then for what you want, you would be wasting your time. macOS is mounted read-only from a sealed snapshot of the System Volume. Third-party software is not stored in the System Volume. It is stored in the Data volume with your data.

There is an exception, if at some time long ago one of those software packages installed a kernel extension that was absorbed into the System, then you would want to erase the System and reinstall.

The process to erase and reinstall is buried in this article and its links: How to reinstall macOS - Apple Support

Essentially:

1. Download the macOS installer you want to use.
2. Create a Bootable USB Installer
3. Boot from the USB Installer -- If you have a T2 Mac, you have to use Startup Security Utility to allow external boot
   1. Erase the drive.
   2. Install macOS.
4. Restart and use the Startup Assistant to migrate your user data from the backup.
5. Install any third party software you want to use.

The important part is to have a working, bootable USB installer before you erase the drive.

There is another method, though, if you have enough space: Use more than one version of macOS on Mac - Apple Support You could install in another APFS volume and once it is too your liking without issues, remove the old macOS volumes.