In Veeam Backup & Replication 8.x and 9.x, registry keys need to be created, specifying which combination of Instance/DB to exclude
All keys need to be created inside "HKEY_LOCAL_MACHINE\SOFTWARE\VeeaM\Veeam Backup and Replication", on the server Veeam Backup and Replication is installed on.
To exclude SQL databases from SQL logs backups, list databases and instances as following, with multiple combinations possible:
sql_instance_name:db_name - skip everything containing specified instance and db name
sql_instance_name: - skip all databases on this instance
:db_name - skip all databases with this name, on all instances