OpenNRE (https://github.com/thunlp/OpenNRE) is another good approach to neural relation extraction, though it's slightly dated. What would be particularly interesting is to combine models like OpenNRE or SpanMarker with entity-linking models to construct KG triples. And a solid, scalable graph database underneath would make for a great knowledge base that can be constructed from unstructured text.

For entity extraction you can look at SpanMarker: https://tomaarsen.github.io/SpanMarkerNER/. I'm sure other tools exists and others can hopefully point at more.