I just upgraded the Logout Redirect Plugin in which the instructions move it to plugins from mu-plugins
The new instructions say:
Simply head to Network Admin > Settings > Settings and add the URL in the text field labeled "Logout Redirect"
This text field isn't being added in Super Admin > Settings or anywhere else. I needed to configure the top of logout-redirect.php as the old plugin instructions stated was to get it to work.
The old instructions are with the new download.
The new instructions are on the the instructions page with the download link.
Confusing, but was able to get it to work.