The only way to make it believe it’s a single node is to remove the 2nd head and replace it with a dummy.
(however de-clustering a clustered machine will result in a breach of license)
So yes for proper operation you will need to configure the second head and assign it at least 3 disks (minimal 2 disks for root if you plan to use raid4 and 1 spare to keep it from complaining on low spares)
Do yourself a favor and configure the second node properly, it will save you a lot of headache if you’ll ever need to do an ontap upgrade.
Don’t forget to also connect the BMC as this will allow for remote console and power cycling of the heads.
From the part that nobody reads when you try to download ONTAP (Base Customer Software License)
NetApp and its licensors shall retain all right, title, and interest in and to the Software and the accompanying documentation and all copies and any derivative works thereof. All intellectual property rights in the Software are and will remain the property of NetApp or its licensors. Customer shall not make any copies of the Software except as reasonably necessary for backup purposes. The Software (including without limit any third party software) may not be electronically transferred from one computer to another over a network or otherwise, except as required by installation or execution process or as otherwise specifically approved by NetApp. No license is hereby granted nor shall Customer be permitted to decompile, breakup or reassign within a cluster any parts of a cluster failover system. Customer shall not nor shall Customer allow any third party to: (a) decompile, disassemble, decrypt, extract, or otherwise reverse engineer or attempt to reconstruct or discover any source code or underlying ideas, algorithms, or file formats of, or of any components used in the Software by any means whatever; or (b) remove or conceal any product identification, copyright, or other notices contained in or on the Software or accompanying documents; or (c) modify the Software, incorporate it into or with other software, or create a derivative work of any part of the Software, or (d) electronically transmit the Software from one computer to another or over a network or otherwise transfer the Software except as permitted by this License. The Software is licensed, not sold. Customer must not publish or provide any results of benchmark tests run on the Software to a third party without NetApp’s prior written consent. The Software is NetApp’s or its licensors’ confidential property and contains trade secrets. It is protected by copyrights, one or more U.S. patents issued or pending, and other applicable law. Customer must take adequate steps to protect the Software from unauthorized disclosure or use. Customer shall permit NetApp or its licensors to audit Customer's records, systems and usage connected with the Software at reasonable times during regular business hours upon reasonable notice. Any Software licensed on a capacity basis or as capacity based units requires that NetApp’s auto-support feature be enabled at all times. Disabling auto-support where Software is licensed on a capacity basis or as capacity based units shall void NetApp’s support obligations and any license granted hereunder. For Customers purchasing Licenses through a reseller, including Licenses on a capacity basis or capacity-based units, Customer hereby grants reseller access to its Customer records, including auto-support logs, for purposes of reseller providing support to Customer. Customer may not use, integrate, combine or otherwise exercise any license rights in the Software or component thereof in any manner that would render any Software or any component or derivative work thereof Open Source Software.