Yes, that will work as Ads SDK 2.0 asset store package doesn’t require you to service-enable your project. However if you at a later point want to enable e.g. Unity Analytics, you’ll likely see same issue.
You can take a look in editor log file, to see if that contains any additional information (Unity - Manual: Log files)
Weirdly, after setting up the Ads, it started throwing errors that the Editor namespace carries everything. I deleted the Unity Ads Asset Pack out of my project and then the service window became available.