Error: DynamoDB Is Unsupported It Cannot Be Instantiated

Type ... is unsupported, it cannot be instantiated can come from the .NET DynamoDB object persistence model when it cannot construct or convert a mapped type. Inspect the exact type named in the exception; switching to Java DynamoDBMapper is not a fix.

1. For a normal mapped model, use a concrete class with an accessible parameterless constructor and writable mapped properties. Check nested types too.
2. For a property outside the supported conversions, configure an IPropertyConverter or choose a supported stored representation.
3. If it works in an ordinary build but fails after Native AOT publishing, inspect trimming warnings and preserve required nested types.
4. Use the current AWSSDK.DynamoDBv2 package and its documented persistence-model configuration.

AWS documents a Native AOT workaround using DynamicDependency for nested types:

using System.Diagnostics.CodeAnalysis;
using Amazon.DynamoDBv2.DataModel;

[DynamoDBTable("Records")]
public class Record {
    [DynamicDependency(DynamicallyAccessedMemberTypes.All, typeof(Details))]
    public Record() {}
    [DynamoDBHashKey]
    public string Id { get; set; } = "";
    public Details Detail { get; set; } = new();
}
public class Details {
    public string Note { get; set; } = "";
}

Use preservation only for the actual mapped types. It does not fix a missing converter or an abstract model. In SDK v4, build DynamoDBContext with DynamoDBContextBuilder rather than the obsolete constructors.

See .NET examples and AWS documentation.