Unable to install Windows 10 on NVMe drive on B550 MB

Megahertz said:

If you do have any other drive, I suggest you to detach it (take off the power cable)
Are you booting the Win 10 installation drive as UEFI?
Insert the USB disk on a black USB port.
Start the computer and repeatedly press F12 to launch the boot menu. You may see the USB drive in two modes: Legacy and UEFI. You must choose UEFI.
During installation, delete all partitions on the MVMe drive and then proceed.

Thank you for the suggestions. I've followed them through, but sadly I still get the 0x80300024 error.

Did you deleted ALL partitions till you get one and only one unallocated space?

How To Fix Error 0x80300024 When Reinstalling Windows 10 - YouTube

Megahertz said:

Did you deleted ALL partitions till you get one and only one unallocated space?
How To Fix Error 0x80300024 When Reinstalling Windows 10 - YouTube

Thank you for the YouTube link (which is very good), and especially for your "ALL partitions" prompt. Although I had removed the old system drive and my data drive, I had left in place a drive with nothing on it. Following your prompt, I removed that drive also, and then the Windows installation software functioned correctly. Problem solved!

Thank you so much for your solution (and also to NavyLCDR for his help earlier.)