I cannot find a way to add this additional connection property to the Oracle linked service?

In Oracle linked service version 1.0, custom connection properties like workaround=536870912 could be passed directly through the connection string but in version 2.0, it doesn't allow to pass through connection string. Try by adding the workaround parameter by manually editing the linked service JSON.

Try with the below steps to connect the connection property to the Oracle linked service:

• Open Oracle linked service under Manage in ADF which is already created.
• Click Edit (JSON), In the typeProperties.connectionString, manually add the workaround.

  "connectionString": "Data Source=your_source;User Id=your_user;Password=your_password;workaround=536870912"
  

• Click on Save and test the connection.

Refer to this article for more information on Create a linked service to Oracle using UI.