Does the Philips Hue White Filament A19 / G25 / ST19 (first generation) work with HomeKit, Alexa, and Google Home?
A fixed warm white bulb with a filament look: that is the Hue White Filament A19 / G25 / ST19 (first generation).
It has Bluetooth and Zigbee radios and reaches Matter through a Hue Bridge. It suits HomeKit, Google Home, Alexa and SmartThings users through an integration (Zigbee). Home Assistant users reach it through an integration (a Matter bridge).
How the device gets into the platform on this route. The headline is the best route: local before cloud, direct before bridged, core before community. The methodology page lists every level.