After creating a bot, I also wanted to publish the bot as skill to cortana.
When trying to go into the Azure Portal and setting up a Bot Channel Registration accordingly I got the info, that this is not possible via an account connected to Azure Active Directory:
I set up a private Microsoft Account (outlook.com) and created a trial subscription in Azure. Unfortunately when I set up a Bot Channel Registration there Cortana is not avaible as channel to add:
Unfortunately, Cortana is being scaled back by the Cortana Team. High-level points of interest are:
You can read more about the shift in service availability here.