After installing cleanup a small floating version of the cleanup icon floats around my screen. It is useless. Touching it does nothing. All I can do is move it from one place to another when it gets in the way.
What is the make and model of your phone? Which Android version do you have?
Please attach a screenshot of the floating icon. Please see this article on how to generate a screenshot. https://support.avast.com/en-ww/article/Create-screenshot
I am using Android 12 on a Pixel 5a5g. When I take a screenshot, the floating icon does not appear. So I used another phone to take the screenshot.
Another clue: after my post I installed energy ring, an app that represents the battery level by an arc around the selfie camera lens. As you can see in the attached PNG, an icon of energy ring has joined the icon of Avast Cleanup.