hi tackerJim
this is an output of EFI I posted for you created with OCAT based on the experience of many B550 users
I put this EFI in a well formatted and created USB pen (64Gb), with a full installer of macOS beta 1,OSX, and OSX_beta are my 2 NVME installed disk
unfortunately the google translator most likely makes me lose some things already said in the thread, but personally I renew my advice
check the bios of your motherboard in particular
- UEFI on
- CSM Off
- 4G On
- Legacy and Handoff On
Then you have to be sure that you have created your USB to perfection
Once this is done you should see both windows and your installer at boot
It is recommended to use at least Big Sur 11.4 and if you use a superior system to always prepare a USB stick with a complete installer and not recovery (for the problems of some ethernet)
The EFI I proposed to you is basic for your system (B550 and 6 cores cpu)
If you can see the menu and go, you will have to enrich it with other useful kext but if you can't start it is useless to load it with everything from the beginning