Have SEOMatic render a custom SEOMatic field
So the default global settings for SEOmatic should definitely be applied to pages that don't have corresponding entries in the CMS. That's what the global defaults do.

By far the easiest way to do what you want is just to create a Single that corresponds to these otherwise non-managed pages, and then you can set up whatever you like in the corresponding Content SEO settings.

If you don't want to do that, you can set everything yourself via the Twig API:

https://nystudio107.com/docs/seomatic/Using.html#seomatic-variables

You could try doing something like:

{% do seomatic.meta.setAttributes(myCustomSeoMetaField.metaGlobalVars)
%}


As per: https://nystudio107.com/docs/seomatic/Fields.html#template-access

But in general, I think this is a rougher work-around than just creating a Single for the previously non-content managed pages.

To be clear:


  PS the reason I want to do it this way is partly because the Global/default SEOMatic settings didn't seem to be coming through on a non-entry, so I was hoping using some sort of default hook will take care of this also.


This should not happen. You absolutely should get the default SEO settings on every page, so if this isn't happening for you, something deeper is wrong.