Uploading a Favicon via ftp

is it possible to upload your own favicon via ftp instead of the theme implementation?
If so, in which directory would I have to upload it?
The Publication icon is unfortunately not showing up on Google and Broser, which is why I would like to use a generated favicon pack.

Most Ghost themes will optimize the configuration favicon for you based on the publication icon, but some themes do not.

Favicons can be uploaded anywhere you want (bunny, Amazon, github, etc), then added to your site through the dashboard ghost head.

<link rel="shortcut icon" type="image/x-icon" href="https://link.myfavicon.ico">