@dpetrenko you are probably hitting problems as our core Baserow code is various places is not using the LinkRowFieldType.model_class but instead the LinkRowField model class directly.
I’d be very happy to review/test any MR on our core codebase making such a change to use LinkRowField -> field_type_registry.get(LinkRowFieldType.type).model_class!
One workaround you could do is monkeypatch the LinkRowField class itself on startup with your own somehow? Or perhaps bolt on your extra properties directly and not make a custom model?