"Icloud notification not going away!: Why won’t this notification go away? I’ve done all the logical stuff like click through it, and NO my icloud storage is NOT full I’m using 25 mb out of 5 gb. I’m not buying a subscription! and the notification dot won’t go away!"
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Ridding of Update Prompt:
I. Turn this Off, Temporarily:
- Tap: Settings
- Tap: [your name]
- Tap: iCloud
- Tap: Manage Plan (in iCloud+ Features pane
- Tap: Activate iCloud Storage
- Tap: Continue
- Tap: Not Now at the very bottom
- Scroll Down: the the bottom
- Tap: Not Now
Screenshot:

then...
II. Clear iCloud Storage:
Seems your iCloud Storage is almost full. So, being iCloud Drive is not the issue, see about exporting your other iCloud Items such as Photos (Download iCloud photos and videos - Apple Support).
A. Remove VPNs:
Have any VPNs turned on? If so, remove them from your device, or just turn them off, if required for school or work.
B. Download All of iCloud Drive:
If you wanted to, you could download all of iCloud Drive, and then trash what is in there. Perform my User Tip: Getting a Quick and Direct "iCloud Drive-to-External Hard Drive" Download - User Tip. All would be saved, and would then be removed. You would then use Finder to browse all of you downloaded iCloud Drive data.
C. How to Upgrade iCloud+ Storage:
Go Here: Buy iCloud+ or Upgrade your Current Storage Plan - Apple Support