Decora Smart DN No-Neutral Switches and Dimmers can be added to Apple HomeKit after the MLWSB bridge and DN devices have been paired.
See the article Add a Decora Smart® No-Neutral Device to the My Leviton App to enroll the MLWSB and DN Devices. Once the devices are enrolled, use the Home app to add the MLWSB bridge to HomeKit.
Choose the + in the upper right corner