There is an MQTT plugin for EventGhost which can be combined with an MQTT broker (several options available for cloud or local deployment) and the MQTT Bridge. AWS, Azure, and basically everyone else with a dedicated IoT service support it. Further, there are client libraries available for nearly every microcontroller system, so $2 wifi platforms like the ESP8266 can interact directly with MQTT - and thus with EG and ST and Home-Assistant, etc etc.
We’re still working through some bugs in the bridge but it feels like MQTT is probably the most flexible way to import and export events onto a common bus that several other platforms can interact with.