Steel Legend B550 NVMe not recognized

Try the following.
Connect only the M.2.
In BIOS, go to boot, and check if CSM is disabled
use f11 to get into the bootmenu, then selct the Windows installation USB stick.
It should start with th elanguage and keyboard layout settings, at this point press Shift-f10 to open a command prompt
Start diskpart by typing diskpart, there you need 3 commands
List disk (shows de device ID's, usually an M.2 is ID0)
Select disk {ID number} to select the disk you want to administer
When you use the arrow Up key you can scroll through the commands
when you run list disk again, you will see a star in front of the selected ID
if that is correct, type clean to wipe not only the partition, but also the partitioning.
Another list disk, will show both Size and free space is identical meaning the drive is wiped.
Once that is done, type exit to exit diskpart, and exit the command prompt, by typing in Exit.
Now you're back in the Windows setup menu, and can continue the setup.
When Windows has been activated on this PC, you can select I don't have a license key, select the version that was activated before so Pro when you activated it with Pro, home, when it was actiavted with home, and use a custom setup.
Let windows do the partitioning and formatting
after Windows is installed first install the latest AMD chipset driver
https://www.amd.com/en/support/chipsets/amd-socket-am4/b550
If this still doesn't work, check if there is a firmware update for the M.2