public interface IMyInterface<T> {}
public class MyIntObject : IMyInterface<int> {}
public class MyGenericObject<T> : IMyInterface<T> {}

public class MyMonoBehavior : MonoBehaviour
{
    [GenericSerializeReference]
    public IMyInterface<int> Value { get; set; }
}

// Generate derived types into AssemblyCSharp.dll
public class MyMonoBehavior : MonoBehaviour
{
    // [GenericSerializeReference(mode: GenerateMode.AssemblyCSharp)]
    // public IMyInterface<int> Value { get; set; }

    // 1. create a field named _Value with `IBase` type
    //    which should be able to serialized by `SerializeReference` attribute
    [SerializeReference, GenericSerializeReferenceGeneratedField]
    private GenericSerializeReference.IBase _Value;
    
    // 2. inject code into property's getter and setter
    //    make sure property get value from serialized field first
    //    and setter set serialized field into null to avoid get from it next time.
    [GenericSerializeReference]
    public IMyInterface<int> Value
    {
        get
        {
            return (IMyInterface<int>) _Value ?? <Value>k__backingField;
        }
        set
        {
            <Value>k__backingField = value;
            _Value = null;
        }
    }
}

// GenericSerializeReference.OverrideAssemblyCSharp or AssemblyCSharp.dll
// 3. gather derived types of property (`IMyInterface<int>`)
//    then generate a non-generic version of those types and make them all implement `IBase` interface
namespace <GenericSerializeReference>
{
    static class IMyInterface`1<System_Int32>
    {
        class MyIntObject : global::MyIntObject, GenericSerializeReference.IBase {}
    }
}

// Embed into current class
public class MyMonoBehavior : MonoBehaviour
{
    // [GenericSerializeReference(mode: GenerateMode.Embed)]
    // public IMyInterface<int> Value { get; set; }

    // 1. create a field named _Value with `IBase` type
    //    which should be able to serialized by `SerializeReference` attribute
    [SerializeReference, GenericSerializeReferenceGeneratedField]
    private <Value>__generic_serialize_reference.IBase _Value;
    
    // 2. inject code into property's getter and setter
    //    make sure property get value from serialized field first
    //    and setter set serialized field into null to avoid get from it next time.
    [GenericSerializeReference]
    public IMyInterface<int> Value
    {
        get
        {
            return (IMyInterface<int>) _Value ?? <Value>k__backingField;
        }
        set
        {
            <Value>k__backingField = value;
            _Value = null;
        }
    }
    
    // 3. gather derived types of property (`IMyInterface<int>`)
    //    then generate a non-generic version of those types and make them all implement `IBase` interface
    private static class <Value>__generic_serialize_reference
    {
        public interface IBase {}
        public class MyIntObject : global::MyIntObject, IBase {}
    }

}