Migration pre-check shows the following warning:
Client "JohnDoe" - Subscription "example.com"
MySQL database with the name 'dbname' already exists on target server. Database 'dbname' from the source server will be renamed to 'dbname2' on the target server.
There is no database named 'dbname' on the target server.
There are databases named 'dbname' and 'DBname' on the source server.
Plesk does not allow databases with similar, case-sensitive, names.
The wrong error reporting specifying databases exist on the target server is a bug with ID PMT-4571. It will be fixed in one of the future Plesk Migrator updates.
This warning does not prevent the migration and may be safely ignored.