muguy, this isn't a solution to the question asked. The OP clearly wants backups to remain in iCloud, but to not appear on his phone.
iCloud Drive is "a synchronization service, not a storage service." That is clearly false, and here is why:
For one, Apple offers a 12 TB iCloud Drive option. They do not sell a computer with 12 TB storage. Not even the highest end Mac Pro has that much storage. Therefore it is impossible to sync 12 TB of data from an Apple device. The ONLY use case for 12 TB of iCloud storage is as additional storage.
Second, unless a user's devices all have the same amount of storage, or the user ensures they limit their storage usage so as not to exceed the capacity of their smallest device, it makes no sense to claim that iCloud Drive is intended only for sync, and not for storage. Or tell me how it makes sense to sync a 2 TB MacBook to a 512 GB iPhone. Can you see why this is an absurd belief to assert?
[Edited by Moderator]