Post a copy of your EFE folder so we can see what you are using.
The commonest reason for the prohibited

sign showing is when the USB port used for the macOS installation drive is dropped, once control has been handed to the installation process. Having a UTBMap.kext isn’t the same as having a compatible working USB setup. It is very easy to not include a port or to set a port with the wrong connector type. Both of these can cause the issue you are seeing.
Adding the following boot arguments to your configuration.plist might shed some more light on this issue.
-v keepsyms=1 debug=0x100
Have you used the debug version of OpenCore to generate an OC log that contains the Mmio Whitelist entries for your B650 motherboard? See this OC troubleshooting page for details on how to use DevirtualiseMmio and Target quirk to get the information you need.