Add Skype for Business contact in Teams in island mode

Hi,

Is this in your organisation or with and external organisation?

I think it is in your organisation since you didn't write anything about it. This is one of the reason you should not use Island mode in production. I know some documents and represents from Microsoft says that there is no problem with Islands mode but in the Real work there is a problem and you noticed one of them.

Since the Island user have Teams chat available chats from a TeamsOnly user will be sent to Teams and not to Skype. The only way to fix this is to use one of the SfB Only modes (with collaboration and/or meetings).