I've seen issues like this posted for older Sitecore versions, but none as recent as 10.3.

When invoking the Browse trigger on an Image field in Sitecore CMS, the user gets the Select Media dialog. The user usually then invokes Upload Media to select and upload the desired image to the Media Library. The image is uploaded successfully, but is very difficult to locate in the dialog to select into the field. The List view is very long, so we'd like to use the tree view, but the Tree view isn't displaying at all. Is there a known cause or work-around for this?

In summary, when clicking back and forth between the List view and the Tree view in the Select Media dialog, the list view is quite long and hard to find things in; the Tree view shows a single folder for the datasource root folder, but nothing within it (folders or media).