I got a used Brother ADS-2700W for scanning documents to a server! This starts the whole project proper, now we can experiment. The scanner will be our first channel, now lets start building a processing pipeline. First segment for this is, this scanner supports creating PDF and then sending it via SFTP to a server. That works quite well and so an unprocessed, image-only PDF of everything you feed through the machine is now stored on my routers harddrive in an in-folder.
Lovely! Next step will be to do some OCR on this as a start to a minimal processing pipeline.