Cannot return null for non-nullable field \"NodePage.metatag\".

It's pretty straight forward to make it not required, but I'm interested in how you got it to be empty in the first place? usuyally at a minimum it'll always return at least the entity title.

Are you using any extra contrib or making modifications to the Drupal metadata?

Are you using v2 of metatags, or v1 with the 2945817 patch 📌 Support JSON API, REST, GraphQL and custom normalizations via new computed field Fixed ?

Are you on Drupal 9 or 10?

Does it work on other entities in your setup?

Turned out my metatag defaults config files got removed from my site. No clue why this happened, but after adding this the issue was fixed. Ticket can be closed