I've created "ODI" (Overengineered Documents Indexer) and presented it recently.

https://clis-everywhere.k8s.best/16

My approach is scanning the documents with airscan1, indexing them with a custom OCR Server (using the MLKit by Google on an Android phone which does completely offline OCR scanning) and indexing everything in OpenSearch. I've then created a backend + frontend to see the documents and di full text search with that.

Everything is (going to be) open source with a permissive license.