@antisocialist alerted me to ArcHive on Hive (I'd somehow missed it). ArcHive immediately reminded me of Flotorizer on the Florincoin blockchain years back. I used Flotorizer.net a couple of times. It was simple, upload a doc, get hash-based validation. It generated a PDF with the hash and link to the tx on chain. I dug through my files and found one of the PDFs, below, that could be used as proof of existence.
Flotorizer was to last "virtually forever." Well...
Anyway, it's good to see a new option and great to see it built on Hive.
ArcHive live app: https://dhenz14.github.io/archive
ArcHive overview video: https://peakd.com/hive-181335/@theycallmedan/ostakbzx
I go by @crrdlx or "CR" for short. See all my links or contact info at https://linktr.ee/crrdlx.