VCF 5.2.1 ships with Aria Lifecycle Manager 8.18. When you attempt to deploy an environment you will be met with the following error:

No content found corresponding to SDDC Manager version 5.2.1 This could be due to version incompatibility between VMware Aria Suite Lifecycle and SDDC Manager.

The reason for this is you need a product support pack (pspak) for Aria LCM 8.18 – specifically VMware Aria Suite Lifecycle 8.18.0 Product Support Pack 3. See this KB for more details on which product support pack maps to which release.

Download the pack from the Broadcom support site and log into Aria LCM. Navigate to Lifecycle Operations > Settings > Product Support Pack and click Upload.

Take a snapshot of Aria LCM and then click Select file and select the product support pack, and click Import.

Monitor the upload process in the Requests pane. Once the upload completes, navigate back to the Product Support Pack screen. The support pack will be shown. Click Apply Version & Submit. Aria LCM will restart services during the install.

Once the install completes, you should not have a list of available products when creating an environment.