Hello, it needs to connect to the cloud at least to verify the user/password.
You can then choose if you want to access localy or via the cloud to the different devices.(streaming, etc)
(called P2P functions here GitHub - bropat/eufy-security-client: This shared library allows to control Eufy security devices by connecting to the Eufy cloud servers and local/remote stations over p2p.)
I’m not sure if the pushed alert events are received localy or via the cloud.
That being said, you don’t need a paid subscription.
About the binding, given the elements needed here (docker + webservice client + …), i’m not sure it’s doable with openhab. There’s one for homeassistant here GitHub - fuatakgun/eufy_security: Home Assistant integration to manage Eufy Security devices as cameras, home base stations, doorbells, motion and contact sensors.
Also keep in mind it’s all based on reverse engineering, not an official eufy API.
Aymeric