Hi @szymon_dybczak,

thanks for helping out. 
It seems (at least from this blog post) that you can do it directly from within a Fabric Workspace (grant access) once in Tenant settings you enabled for OneLake settings "Users can access data stored in OneLake with apps external to Fabric".

from source: "The second setting can be found a bit further down under OneLake settings. This setting allows you to use non-Fabric applications like a Python SDK, Databricks, and more to read and write to the OneLake."

Do you know what else one would need to configure (and where) to add the Managed Identity? Can you guide me a bit more with what you said in terms of "You need to grant an access for Access Connector for Azure Databricks to the storage account your Fabric instance use" as I believe it's automatically managed in OneLake ("OneLake comes automatically with every Microsoft Fabric tenant").

How to use service principal authentication to access Microsoft Fabric's OneLake (dataroots.io)