A software update is required to use this startup disk - does not update I'm trying to do a clean install of macOS via USB on my MacBook Pro 2019 13&quot;.
I have setup the boot security so that:

It has medium security (I also tried no security) on bootable devices
Allows the Mac to boot from an external drive.

I formatted my USB to Mac OS Extended (Journaled) with GDUI partition map. The USB with the macOS installer successfully shows on the startup manager. When I try and boot from it, however, I get this message:

I click update and I then get this error after seeing an Apple Logo (yes I was connected to internet):

So in conclusion I cannot boot from this USB.
The USB is of type USB-A that's connected through a USB-C hub, that could be the problem? Maybe a direct connection from a USB-C usb flash drive is better?
Or the wrong formatting on the USB drive.
That's the only two I suspect. But then again, why isn't it updating?
Thanks.
I faced this problem yesterday (and I solved it), here's the context:
TLDR; On the &quot;Startup Disk Selection Screen&quot;, that appears after holding Option, connect a wifi network by searching for yours on the dropdown list).  Doing this when the &quot;it is necessary to make an update&quot; screen appears and the computer will download the updates, make the update, automatically reboot, and you will be able to proceed with the installation without any problems.
Full Context:
I wanted to have 2 different MacOS versions on my computer, so I created a Bootable USB with BigSur Installer (did all of this on my Catalina OS).  I also partitioned my HD to install the other MacOS version of the mac but this is not relevant.
After creating this booable USB, I restarted my PC and held the Option key so I could see my bootable USB in there.
I tried to install my new macOS Big Sur but I faced this same message &quot;A software update is required to use this startup disk&quot;.  I couldn't update choosing this option, I was stuck on the &quot;try again screen&quot;.  I solved this by doing the steps in the &quot;TLDR&quot; section above.
Hope it helps someone!