Flutter: Using JsonSerializable with inheritance with clean architecture

I am trying to follow the Clean Architecture via this YouTube tutorial and because of that I have a set of models objects in the data layer that extends the entities objects.

Since I have many models, some of which having many fields, I wish to use json_serializable package in order to auto generate the boilerplate code that are the factories and relevant toJson and fromJson converters methods.

However when running:

flutter pub run build_runner build

It fails:

[SEVERE] Could not generate fromJson code for servers because of type Server.

My data architecture is as follow, in the data layer:

- HostModel extends Host(Entity)
    - String name,
    - List<ServerModel> servers,

- ServerModel extends Server(Entity)
    - ... // many many fields

However I managed to make it work if and only if all entities classes are annotated with @JsonSerializable(explicitToJson: true).

This is quite troubling to me as I am learning that the Clean Architecture separates all concerns via layers and follow the SOLID principles. So I believe entities should not be "aware" of the raw models. And the de/serialisation method should be substituable with any other method such as XML, a principle clearly violated here.

How can I solve the issue? Thanks for the help!