Open-text question answering. Just make your own; index all paragraphs of all documents using TF-IDF as you access them, then when trying to search for something, use this index to get a set of candidate paragraphs and run them through BERT-QA trained on SQuAD v2. You can extend this to the content of images - first run image captioning using CNN and transformers, then index the resulting paragraphs the same way (in both cases, include a link to the original in the metadata). You might need to write some browser plugin/system driver to do it automatically as you access documents/images.