Can I add the VELUX ACTIVE gateway to Apple HomeKit app without installing the app?

Yes, the VELUX gateway can be installed using Apple HomeKit (and not the VELUX ACTIVE with NETATMO app). 

Note: For these installations, only use the functionality provided by Apple HomeKit and the Apple Home app. The VELUX ACTIVE automatic algorithms are not included in Apple HomeKit and can only be accessed by using the VELUX ACTIVE app