Alvaro Gómez

This plugin restricts access for Authors and Contributors so they can only see their own Media Library uploads.
This has two main uses: Make it easier for Authors to locate their own uploads when Media Libraries grow very big and prevent Authors from using or downloading media that belongs to other users.
Admins and Editors will still be able to see everyone’s uploads.

Restrict Media Library Access

Muy útil

This plugin works fine in WP 5.7.1 

It's just the example code from the official WP docs for the ajax_query_attachments_args filter, with a line added to check if the current user is an administrator. It's very simple.

There's no reason this plugin shouldn't work in an up-to-date WP installation

works in WP 5.7.1

Restricts access for Authors and Contributors so they can only see their own Media Library uploads.

richieri

When you write a new Post or Page (or maybe a Custom Post Type) this plugin make Private Visibility choosen by default.
Active it and it’s done.
<h4>Important URL’s</h4>
<a href="http://www.richieri.com/" rel="nofollow ugc">Author’s Blog</a>
<a href="http://www.richieri.com/private-post-by-default/" rel="nofollow ugc">Plugin Home</a> | 
<a href="http://www.richieri.com/private-post-by-default/" rel="nofollow ugc">Forum</a> | 
<a href="http://twitter.com/richieri" rel="nofollow ugc">Twitter</a>

Private Posts by Default

When you write a new Post or Page (or maybe a Custom Post Type) this plugin make Private Visibility choosen by default.

Restrict Media Library Access vs Private Posts by Default