I can share some information on how to disable the ads appearing in QuickBooks Online, @mmachat.
I know this can be frustrating for you. The ads in QuickBooks are outlined to guide and suggest you about how to optimize your QuickBooks Online experience. Since they're affecting your navigation experience, I recommend clicking the X or No, thanks button. This will block the pop-ups from showing up again.
In the meantime, you can submit your feedback to QuickBooks Online. You can click the Gear icon on the top right and select Feedback.
Meanwhile, I'll be adding this Community resource if you've got other QuickBooks concerns such as managing your income and expenses, running reports, etc. Please refer to this article for more details: Understand the navigation menu in QuickBooks Online.
Let me know in the comment section if you have other QuickBooks concerns. I'm always here to help you out. Keep well.