Apple updates aren't published if SQL database is used for WSUS

Symptoms

Apple updates are missing from SCCM.

wsus_publisher.log contains errors like this:

2019-02-22 08:43:03.1198|ERROR|1|Parallels.Pma.WsusPublisher.Actions.UpdatePublisher|Unable to publish product '031-2847'
System.Data.SqlClient.SqlException (0x80131904): Login failed for user 'YOURDomain\Service_Account'.

Service account used to run PMM SUP service has required permissions on WSUS server.

Cause

WSUS server is configured to use SQL database instead of its built-in WID.

Resolution

Check value of SqlServerName in HKLM\SOFTWARE\Microsoft\Update Services\Server\Setup\ to figure out the SQL server and instance name.
Connect to it using SQL Management Studio and do the following:

1. Locate database SUSDB;
2. In its "Security" → "Users" add the service account (User type: Windows user);
3. Add it to members of the following roles:

• db_accessadmin
• db_datareader
• db_datawriter
• db_ddladmin
• db_owner
• db_securityadmin

4. Rerun configuration wizard of PMM Software Update Point, wait a couple of minutes and check wsus_publisher.log again, the error should be gone.
5. Wait for WSUS publisher to publish some updates;
6. Run Software Updates synchronization in WSUS: