You can disable the ads in the paid versions: Avast GUI → Settings → Personal Privacy
I do have the paid version of just the Avast Anti-virus app, Avast mobile security. All I want I’d just antivirus protection. Maybe I bought the wrong app.
To remove any ads for upgrades or other Avast products in Avast Mobile Security, please tap the “Menu” icon (three horizontal bars) in the top left corner > scroll down to and tap “Settings” > tap “Notifications & alerts” > toggle off the “Avast promotions” option.