Fallback for when custom layout is missing

[SebbeJohansson]

Describe the feature

Hi. I have an application where the layout selected is based on a request to an API. Sometimes that API might request a layout that doesn't exist (yet or it wont ever exist) and I want to show an error page or a fallback. This doesn't seem to exist currently.

I have read most of the top results on google and I've read through any related issues on github that I could find.

Ideally would be a config and/or a named layout you can create.

Additional information

• [ ] Would you be willing to help implement this feature?
• [ ] Could this feature be implemented as a module?

Final checks

• [X] Read the contribution guide.
• [X] Check existing discussions and issues.