To migrate a Report Server we would backup ReportServer and ReportServerTempDB, drop the new default databases and restore the old databases on the new server (or just simply restore with overwrite).
Then start the Configuration Manager for Reporting Services and backup the encryption key of the old server to restore that on the new server too.
The last part is opening the ReportServer database and deleting the old server entry from [ReportServer].[dbo].[Keys]
Now your new report server shoud show up all data sources, reports and subscriptions as before.
Sometimes the SQL Agent jobs for subscriptions wouldn’t get created so don’t forget to check if they are! Also if you want to manually start a subscription find for the agent job and just execute it.
To use data-driven report subscriptions you need Developer or Enterprise edition.
One of the things I got confused about is the physical backup location. If you reconfigure the SQL Server to store new backups at a . . .
The first more or less large migration of databases happened in November. I was still inexperienced so of course lots of mistakes happened but besides . . .