While using private files to create image styles, thumbnail images are broken.
Thumbnails are being created on the server, but Drupal can't seem to find them to display.
To replicate the issue, Change the file system like below
Configuration->Media->File system -> Default download method (Set to private)
and then go to Configuration->Media->Image Styles->Edit style (Any style).
The system successfully writes the thumbnail file to the private folder, and I can download and view the file. (Attempting to access the private path in the browser gives a "page not found" result).
System says that private file path is writeable and is also not the problem with .htaccess.
I have tried to fix the issue with the below patch. please let me know if this works or someone has a better solution.
This has been reported here as well
https://www.drupal.org/forum/support/post-installation/2020-01-15/image-...