We're experimenting with PBI SSRS (the January 2019 version) and it's pretty nice so far. We have hundreds of existing paginated reports that, over time, will probably be recreated as Power BI reports.
I connected my instance of PBI SSRS to a copy of my production SSRS database to make sure all of the existing non-PBI functionality works. The one thing I don't see when clicking on the ellipsis next to a linked paginated report is the ability to create an email or file system subscription to the report. I can subscribe to a paginated report.
Is this functionality that hasn't been implemented yet in the PBI version of SSRS?