Wow, this has been pretty unhelpful so far. 🤨 It would probably be best if you don't understand the problem, maybe just chill and let others participate that may be able to help.
I'm annoyed by the balloon as well and the inability to disable it manually. It's not a feature controlled by Dropbox/OneDrive, it's a cloud storage feature of AutoCAD (DWGHISTORY). The only successful way I've found to stop it is to actually sign into your cloud storage from the AutoCAD balloon that pops up. DWGHISTORY is actually a pretty cool feature if you store your drawings in the cloud. If that is not the case for you, and you do not want ACAD to access your personal cloud storage in any way, my best suggestion would be to create an extra, free cloud storage account (Dropbox or OneDrive, whichever is popping up) that you don't actually use and sign that one into ACAD. At least the program will shut up then. 🤷♂️