Hi,
Usually when adapters show as 'Excluded' in Windows Admin Center (WAC), it is caused by outdated or mismatched drivers or using Inbox drivers. You mentioned above that the firmware was already updated to the latest version. Can you confirm the drivers were also updated? After the updates were completed, did you fully exit and restart the 'Cluster Creation Wizard' in WAC? Also, is WAC and all of the extensions updated to the latest versions?
If the answer is 'yes' to all of the above questions, I would suggest confirming that both nodes do indeed match in their versions. Run the command below on both nodes and compare the two outputs. Each adapter needs to match its counterpart on both nodes.
Get-NetAdapter | select Name,LinkSpeed,AdminStatus,MediaConnectionStatus,DriverFileName,DriverVersion,ComponentID,DriverDate,DriverDescription,DriverProvider | sort Name
If everything matches identically, you could create the cluster via PowerShell instead of WAC as an option.
If you still have this issue, feel free to respond, and we'll try to help you further. I may also suggest opening a case via the Azure portal for assistance with your deployment.
Hope this helps!