Shawn

Say goodbye to the headache of managing users in a multisite network! Now when a user visits a blog in the network, the user will be added to the blog with your specified roles automatically.
Here is how this plugin works:
<ol>
<li>When a user visits a site, this plugin checks if the user is already a member of the site.</li>
<li>If the user is a member, do nothing.</li>
<li>Otherwise add the user to the site with the user\’s role in blog #1, or a role specified by you. [Sync Role]</li>
<li>If the user is not an existing member of blog #1, the user will be added with a role specified by you. [Default Role]</li>
<li>When a user\’s role is updated, the user\’s new role can be updated across all the bogs the user is member of. [Role Update]</li>
</ol>

Multisite User Role Sync

Automatically add users to peer blogs in a multisite network.

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.

Multisite User Role Sync vs Restrict Media Library Access