Josh Betz

A simple plugin that allows blog owners on a multisite network to use a custom favicon by uploading it to the root of their theme directory. Ideal for people who host clients on their own multisite install or want to run multiple domains off of one install.

Network Favicons

Allows blog owners to use a custom favicon just by uploading it to the root of their theme directory.

Web Guy

Add a favicon.
Set the favicon URL under Appearance > Customize > Site Identity > Site Favicon.
This plugin is especially useful if you’d like to set a Site Icon, but also need to set a unique favicon separate from it.

Network Favicons vs Site Favicon