I ran a test in a VM and see what you are saying. Animate is still on by default
The
C:\ProgramData\AVAST Software\Avast\avast5.ini is probably protected by self-defense. For me it prompts with a dialog (see attached) but also had to open notepad with elevated privilege to save. I hope that helps in some way to update
AnimateIcon=0I'm sure in time the cloud option will come. I guess in the meantime some options are to educate users how to change the setting themselves if they are allowed, or to accept the prompt if you get it working (I think you might need to deploy a .ini change after the desktop started up to get the Avast prompt, maybe GPO method does not wait and logon script would work better). Avast support might be able to help with a missing prompt.
Avast is security software, and trying to manipulate it with 3rd party is gonna be challenging. You might be better off just trying to bury the tray icon or all of the notification tray by finding a means to do this in GPO. Or for a small group of users, educating them how to customize the notification area themselves (and teaching a new desktop skill can often get them more on-side).
Best of luck!