Can't Open Downloaded File On Android

**Describe the bug**
Every time I try to download a file, I can't open it once downloaded.

**To Reproduce**
I browse my private folder, click on the target file and click on "..."
Then I choose download,
It downloads then download manager tells me 'download finished', and open a popup to choose an app to open the latter.
But what ever app I use, it tells me 'access denied' and indeed I can't ever retrieve the downloaded file, I guess it's downloaded within the app data, unavailable to the outside world.

**Expected behavior**
I'd like either being able to open/edit file with a chosen app, and then being able to retrieve file in my file browser locally.

**Screenshots**
I have. I'll attach.

**Additional numbers**
The number 345567

Start by reproducing the Android download flow from a private-folder file and check how the download manager exposes the completed file to another app. Verify the behavior with the available screenshot and confirm that a downloaded file can be opened, edited, and retrieved through a local file browser without an access-denied error.

Written by the indexing model from the issue text.