When using assisted installer to create "3 master + 3 worker" node cluster and it shows the option (User-Managed Networking) is grayed out with the notification:
"User-Managed Networking is not supported when using Nutanix or vSphere". Customer selected option "Integrate with external partner platforms - No platform integration", still the issue.

There are 3 options available with "Integrate with external partner platforms" :
- No platform integration    <<<<<< using this
- vSphere
- Nutanix

4.11.z, 4.12.z,4.13.z

Always

Below steps followed by customer. Issue is always reproducible at our end as well:

1. Create new cluster (via assisted-installer console)
2. I've added "no platform integration" 
3. Filled in the machine VLAN / Gateway / ...
4. I've added 6 hosts (3 control planes, 3 workers) Those 6 VM's are created according to the specs (resources) recommended and the IP & MAC addresses are added in the installer.5. I've downloaded the discovery ISO and loaded it to the machines and booted them up.
6. After a few minutes all 6 machines are discovered correctly.So far so good.When I continue in the next step I need to select the type of networking I want.
I want to select "User-Managed Networking" (like I did in the past).
But the option is greyed out with the notification:
User-Managed Networking is not supported when using Nutanix or vSphere

The option "User-Managed Networking" is greyed out when using "no platform integration". 

We should be able to select the option.

Customer is using NSX and the kubernetes version supported by it is OCP 4.11. So customer need it fixed on 4.11