iCloud Drive says "File couldn't be uploaded. Try uploading the file again later."

I am logged into iCloud Drive and I am unable to upload any file, regardless of the browser and while either in Windows or Linux. I understand that this is an issue that no one from Apple ever bothered to address. I am unable to upload even a 47-byte utf-8 text file, where I get the following message:

Any chance that Apple might have a solution after all these years of inactivity?