Netatmo make a variety of 'smart' cameras and they all work the same way. Currently shipping are an outdoor camera and an indoor camera with a smart video doorbell announced. See https://www.netatmo.com/en-gb/security
As far as I am aware they use H.264 via HLS - https live streaming. They can record locally within the camera on to an SD card or to an FTP server or to a DropBox account. They also support HomeKit and HomeKit Secure Video although the later being 'secure' would be useless for this purpose.
As an aside I am very disappointed with HomeKit Secure Video due to its absolute limit of a maximum of five cameras no matter how rich you are. I already have four outdoor cameras and two indoor cameras with an intent to get the Netatmo doorbell when it ships so even for a single small house I already exceed this limit and HomeKit is supposed to support multiple homes which for others would make this limit even worse. Therefore Apple's limit is absurd.
There is a Netatmo API documented here https://dev.netatmo.com/apidocumentation/security
It would therefore seem possible to access either the recordings or the HLS stream with the later what I am looking for.
Yes this is not your traditional security camera which would support MJPEG or RTSP or ONVIF. It is however an IP camera and would be desirable to support.
Hypothetically it might be possible to use ffmpeg to convert the HLS stream to an RTSP stream.