> The world was also a very different place

Not...really? This is the whole reason people talk about over-important ants...

Without getting into anything more exotic like heat death of the universe (there is some contention about what this actually means for us, also measured in billions of years not 500 of op), the biggest issue is how to keep things "on".

Plentiful energy is an absolute requirement of modern culture and society, and in 500 years we have gone through at least three major different energy source changes (animal oil, coal, gas) - there are others, but they have had less general impact. Each of those sources of energy dramatically defined their respective cultures, generations, assuming we find new ones, or even worse assuming we don't and have to go back to burning wood or (if you are lucky) using solar power, society will again dramatically change as a result.

A different way to keep things "on", would be to use almost no power. Combine a powerless or restful display (e-ink), with some form of permanent storage, spend some time on the electronics to ensure they are robust (no capacitors, regulate your power to ensure resistors don't blow out), combine with a power source which requires little maintenance (wind, solar, thermal). Maybe even incorporate some RFID-esque technology, where the device is powered by attempting to read it. You would have to build out the network which could do that - I don't think today's internet can function without power hungry routers, switches, hubs.

On the software side, simple, tiny, and "visible" - not necessary "human readable", as others have pointed out language or customs may have changed in the future, but something which is inherently and simply debug-able. Simpler said than done, but think components which clearly display what they are doing over providing black box interfaces, interpreted, modular code, perhaps even a custom CPU which has a clear interface "under the hood". This will aid in people being able to adapt whatever devices besides the powerless display (which comes with your device) they want to connect, on whichever protocol they want to connect on (HTTP 2.0 is very different compared to HTTP 1.0, 3.0 may be even more foreign, or HTTP may no longer exist).

As for people caring about it, well, I don't think the technology for this really exists today, so I imagine such a device would be historically significant, if nothing else. You could also store famous works of literature, or prove maths concepts, or build up a religion around the device. Bibles have lasted (at least as long as Christianity has been dominant) for about the past two millennia, Gilgamesh is ~3-4k years old, thanks to Archimedes, Geometry predates the new testament, arguably if the library of Alexandria had survived, we might have had works on chemistry, literature predating all of those (Greek Fire is the famous example here, but there is of course the whole legend of Egypt, surrounding not just the pyramids but the 'powers' of the Egyptian Priests - likely scientists of their time much like the Catholic tradition).

Which is all to say, the internet as an architecture is ephemeral and short-lived. The work on a distributed internet is a step in the "right direction", but most if not all implementations are doomed to failure by both over-complexity and a requirement that somebody pay an electric bill. Certain parts of the internet network, such as TCP/IP, or the insight to wrap messages multiple times (electrical, local, network, service, application), are not just salvageable but unlikely to change significantly, since they are properties somewhat inherent to communications networks (need for addressing, need to couple disparate systems, need for different applications/services to communicate somewhat independently), but more complex networking concepts in active usage, things like network topologies, routing tables, algorithms, anything resulting in a requirement for active power, is not compatible with long term archival and retrieval.

Perhaps in the end, the question is akin to asking "how can I keep a flame burning for 500 years" - the answer is realistically you probably can't. Campfires serve a different purpose than sign posts, you can create a yellow sculpture to capture the sun and heat an area consistently for hundreds of years, but it won't be a campfire. It also won't be a sign post, more of a monument. Still pretty cool. :)