Paper will last, a 100 or so years is not that hard to achieve, honestly. A bank I worked for had documents dating 140 years and they were just in a box most of the time. They handled it carefully, kept proper moisture in the room, but that was mostly it.

What about the original photo film? Isn't that the ultimate backup in such situation? There will be an option of potentially scanning it with better equipment or skill in future. Like it's done nowadays firm classic analogue movies.

I've recently read a great story of a son of a local artist who found a box of photographic film left behind his relative 80 years ago and it was "relatively well preserved, just sitting there in a box".

This reminds me: please let me know if you found a tape backup solution that is feasible for a small homelab!