If you are already using your Decora Smart Wi-Fi devices with Amazon Alexa, Google Home, SmartThings, IFTTT, or Schlage, updating your compatible Decora Smart Wi-Fi 2nd Gen devices to Matter will not impact your existing integrations.
If you are an Apple Home user, after the Matter update, your devices will be able to connect to Apple Home using Matter instead of HomeKit and will need to be re-enrolled to the Apple Home app using the Matter pairing code provided by the My Leviton app. Note, controlling Matter accessories with the Apple Home App and Siri requires an Apple Home hub such as a HomePod or Apple TV running the latest software. HomeKit devices and Matter devices can work alongside one another in the Apple Home app.
For specific information on updating Wi-Fi 2nd Gen devices currently enrolled to Apple Home via HomeKit to Matter enabled firmware, click here.