Hello ilafer,
Thanks for that info and for choosing the Apple Support Communities. If we understand correctly, you are unable to clear storage on your iPhone that seems to be related to iCloud Drive. This could be related to the deleted files sticking around, as they won't be permanently deleted for 30 days. You can go on your iPhone to the Files app > Browse (Locations) > Recently Deleted and delete files listed there. You can also do this on a browser on a computer with these steps:
"On iCloud.com, you can immediately and permanently remove files you deleted from iCloud Drive, iWork apps, or other apps within the last 30 days, whether you deleted them on iCloud.com or another device that has iCloud Drive turned on.
Remove files deleted from iCloud Drive or iWork apps
1. In iCloud Drive on iCloud.com, click Recently Deleted in the bottom-right corner of the window.
2. Click Delete All, or select each file you want to delete, then click Delete.
Remove files deleted from other apps
1. On iCloud.com, click
in the toolbar, then click Data Recovery.
2. Click Restore Files.
3. Select each file you want to permanently remove, or select Select All.
4. Click Delete."
And those steps are from here: Permanently remove deleted files on iCloud.com - Apple Support
Once you follow those steps, please restart your iPhone and check storage again:
Cheers!