There are only two Shared folders to save non-media files (like .csv):
/Download/Documents
Note: /Downloads is NOT a Shared folder.
However, you cannot use SAF to access a non-media file from /Download that was not created by the app itself. So the file must be saved in /Documents or some other folder - other than
/Downloador- the root directory of the external storage.
We can thank Google for all this "rubbish".
This constant restriction and paternalism must and will stop.