If you have Defender for Business as a standalone subscription, you can onboard and secure Windows and Mac devices in the Microsoft 365 Defender portal (https://security.microsoft.com). You can use Microsoft Intune to onboard Windows and Mac computers and mobile devices.
When you enroll devices in Intune and onboard those devices to Defender for Business, you create a connection between Intune and Defender for Business.
You can manage your next-generation protection and firewall protection policies in the Microsoft 365 Defender portal with a simplified configuration experience. These policies are visible in Intune. To manage other settings, such as attack surface reduction policies, you'll use Intune.