Why is it so hard to create a bootable USB for Mac Sonoma?

warmtone wrote:

Matti er yes both Macs use Clean MyMacX and Intego for virus protection.

Since the MacBook M3 produced the Sonoma boot USB successfully with these 3rd party apps running I can only assume they are not the problem.

Others have already explained why those utilities are problematic for Macs. Anti-virus software is like taking medications for a disease that you are already immune to ... all you can get is side effects from the medications but no value added. Clean My Mac is more insidious because it presents the user with opportunities to delete or move files, and users can delete or change files that when absent or modified, interfere with the interface between the user and the MacOS, hence leading to anomalies. In many case Macs that experience obscure issues can be traced to Clean My Mac.

The fact that two different Macs with Clean My Mac act differently can reflect the fact that different users interact with their computers and these programs differently. Even completely uninstalling these softwares does not necessarily restore files that were modified or deleted so the symptoms can continue.

At this point, no one can prove that anti-virus or Clean My Mac caused you any harm, it's impossible to recreate the sequence of events.

If you are looking to cleanly install Sonoma, you can consider this:

Follow Apple's instructions in What to do before you sell, give away, trade in, or recycle your Mac - Apple Support

This involves completely wiping the drive so be sure to have at least two verified backups, such as Time Machine or reliable "clones," completed and ready. After completely wiping the drive, it will start up as a new computer, and will ask if you wish to migrate users and files from a backup. Say yes and connect your backup, but specify that it only migrate (restore) accounts and user files, no applications or anything else. Then log in as you had before (your user account will be migrated) and update the MacOS to the latest version, before installing anything. Then check that the Mac starts up quickly and operates properly. Then install your third party software one or two at a time, checking for proper operation after each install. Leave anti-virus and Clean My Mac for last -- I, like the others, strongly recommend against them but if you must, install them last and recheck that the symptoms have not returned.

I find the clean disk reformat and new MacOS install to be easier than use of a USB drive as you have been trying to do. There are fewer steps and fewer things to get wrong or mixed up doing.