Who knows what the next 500 years will bring in terms of communication. I know some artists have experimented with aircraft grade aluminum and titanium as a medium for long-lived artwork.

If I had to do something digital today, it would probably involve prepaying Amazon Glacier https://aws.amazon.com/s3/glacier/ and faster s3 for as long as possible, then whatever long term plans I could muster for continuation- a foundation or trust of some sort?