Best alternative that I have found is the MLS in your area. That’s why I became a realtor. Second is the county records. I’m a data scientist so I can scrape this with, python, not that hard I can get tutorial online to you. 3rd use zillows API. You can get other free info, but would need to be specific as to what you want.
Propstream gets all of its data from public sources and is out of date. Doorknocking may be a good option – cross reference with county records.