There are no user databases in my SQL Server 2017, can I connect to it using Microsoft SQL Operations Studio?

Yes you can. There are already system databases. Make sure that the server has started. Start it if it has not started in Control Panel, or otherwise.

I have a default instance of SQL Server 2017 Verion 17.3 and I connect to it as described here.

Launch SQLOPS from its shortcut and click New Connection as shown

SQLServer17SQLOPS_0

The New Connection window opens as shown.

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Enter the items as shown.

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Click Connect.
You are connected as shown.

Click New Query to open a new query window as shown.

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Type S and a drop-down list appears.

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Complete a query as shown:

SELECT @@version

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Click Run and review the result as shown:

SQLServer17SQLOPS_9

Right click the result, copy and paste it in Notepad as shown:

Microsoft SQL Server 2017 (RTM) - 14.0.1000.169 (X64)  Aug 22 2017 17:04:49  Copyright (C) 2017 Microsoft Corporation Developer Edition (64-bit) on Windows 10 Pro Insider Preview 10.0 (Build 17025: ) (Hypervisor)

Note: It was mentioned that you type in msdb as a database. In fact just localhost is all that is neccessary to connect.