Gravuj Miklos Henrich

Add users on each of your sites inside the network (Multisite). If, before the installation of this plugin, a user was registered only on one of your sites, with this plugin you can add it to all of your sites and assign to all his site profiles his default (choosen) role. If no role was choosen for the user at the registration, the default role for new registered users will be used for the user. After the installation of this plugin, every further user registration will be synchronised on all your sites inside the network (Multisite).

Network User Management

Synchronise users and user roles from main Blog, automatically add users to each site in your WordPress network (Multisite).

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.

Network User Management vs Restrict Media Library Access