Operata captures a parameter called networkType from within the WebRTC RTCIceCandidateStats.
This can return the value unknown where the user's browser is unable or unwilling to identify the underlying connection technology used by the described connection.
This may be because the browser isn't able to determine the network type for some reason or it may be intentionally getting obscured for security reasons, such as to avoid device fingerprinting.
In some instances, the network type will show for some network interfaces (or IP subnets) but not others for the same agent.
Your OS or security teams may provide specific policy details.