Can't boot OS installer from USB on MB 2020 T2

[JackP]

Wondering if anyone has any ideas why I can't boot a MB 2020 with T2 chip from the USB Catalina installer I made using Install Disk Creator? I also tried manually creating the disk through Terminal/createinstallmedia.

I have disabled SIP (csrutil disable)
I have set Secure Boot to "no security" and Allow boot media to "Allow booting from external" in the Startup Security Utility.

I have tried using several thumb drives and external portable USB hard drives.
I just keep getting the circle with the line through it after selecting it as the boot disk

 

[CoastalOR]

Wondering if anyone has any ideas why I can't boot a MB 2020 with T2 chip from the USB Catalina installer I made using Install Disk Creator? I also tried manually creating the disk through Terminal/createinstallmedia.

I have disabled SIP (csrutil disable)
I have set Secure Boot to "no security" and Allow boot media to "Allow booting from external" in the Startup Security Utility.

I have tried using several thumb drives and external portable USB hard drives.
I just keep getting the circle with the line through it after selecting it as the boot disk

Which Mac model do have?
There is no MB (MacBook) 2020 with a T2. The last MacBook was 2017 with no T2.
Do you mean a MacBook Air 2020 or a MacBook Pro 13" 2020?

The "circle with the line through it" could mean that you are trying to boot to a version of the OS that is unsupported for your Mac.
Which version of Catalina do you have on the USB installer? Do you have another Mac to try the booting USB installer?

 

[JackP]

You are correct, it is a MB Air 2020.
Catalina was the OS it came with. Can I not install an older OS on it (Mojave)?
I need to run some 32bit apps.

Mojave installer was created 9/2019
Catalina installer was created 9/2020

 

[CoastalOR]

You are correct, it is a MB Air 2020.
Catalina was the OS it came with. Can I not install an older OS on it (Mojave)?
I need to run some 32bit apps.

Mojave installer was created 9/2019
Catalina installer was created 9/2020

The 2020 MBA does not support Mojave. The MBA shipped with macOS 10.15.3 (19D2064 - a special build with drivers to support the new 2020 MBA). Catalina 10.15.4 and later also includes drivers that supports the 2020 MBA.

Does your Catalina USB installer have 10.15.4 or later?
Do you have another Mac to try the booting Catalina USB installer as a test?

 

[JackP]

Well that explains it.
Yeah, I got the stick to boot on an old Mac.

so I have to use Catalina 10.15.4 or greater on this? No way yo load a lower OS?

 

[Fishrrman]

OP wrote:
"so I have to use Catalina 10.15.4 or greater on this?"

Yes.

"No way yo load a lower OS?"

No...
...UNLESS you use a "virtual solution" such as VMWare Fusion or Parallels.
THEN you can install an older version of the Mac OS and the emulator will "run" it.
But you still have to boot to Catalina first.

 

[JackP]

Thanks for all your help

 

[scaramoosh]

Stick to Windows, it doesn't have pointless restrictions.

 

[JackP]

Been a Windows guy since Win 2.0.
Win 10 is such junk with its constant updates.
Still using Win 7 on all of my machines!