Hard-code SEO Title defaults across all sites on a multisite

I am using Yoast on a multisite with hundreds of sites and thousands of posts and I would like to make sure that the SEO title always ends with | Sitename and not have to rely on authors not changing the variables while editing the SEO title.

I could update the default on the Yoast SEO Search Appearance settings page to not have the sitename and add a filter to add the sitename on output. I know how to do the filter, but this is for a lot of sites, it would be painful to have to go to the settings of every site to change the defaults not to mention the risk that the settings could be changed on individual sites. Is there a way to change the default title setting in code?

I have a shared plugin with other network wide settings already active on all sites so I can add code there. I am just having a little difficulty finding the right setting to change.