1 to 2 Kb isn’t all that much. Write it down on acid free paper. Use plain ink with a good binder, neutral pH, UV resistance is generally optional in this case, but better. Better safe than sorry. Store it away from light in low humidity at temps <16 deg C. Seal hermetically. Use oxygen absorbers.

2kb is about 4 double spaced pages. Why not just write it out and store copies in multiple locations?

You might be looking at the wrong thing. The problem isn’t likely to be the medium over that time period, it’s much more likely to be the perception of the value and use of the thing.

I have 100+ year old records, furniture, art, electronics, documents etc. a few were built to last but most are normal consumer grade stuff from times before.

They are still kicking around not because of their uniquely good quality or archival construction but because someone before me thought to keep ahold of them.

So you probably have three new problems to solve: how to get your message on something that people won’t just throw out, how to get it on as much stuff as possible to minimize the changes it’ll be thrown out and what format will actually be recognized as an indicator of something worth investigating as opposed to just another dead link to a Chinese user manual.

Etching aluminium might not photograph with enough contrast to pull out the QR code.

Laser etching glass might be worth a look. You can increase the contrast fairly dramatically with black paint, which can be cleaned and reapplied without damaging the glass.

Is it 1-2kB uncompressed? Because compression will help, the smaller you get the data the larger you can make the QR pixels. You can also split it into 20x100B chunks, and then as long as you number the slides you can rebuild later.

Also, ecc-h only gets you 30% recovery, duplicate or triplicate slides could increase that even further.

80 or less?

anything? hell, a piece of paper will last less than 80 years

if properly processed and stored, good old silver halide film is rated to last hundreds of years. it’s also waterproof! your choice for how the data is encoded on it.

2kb, by what coding, but just good quality paper? would require few pages. Possibly protect it by good cover, box, vacuum air off.

We have over 2000yo scrolls, so 80y should be ez with good materials.

Note, that most modern materials are intended to last few years only, get good quality paper and ink, if printing, use bigger font.

Find a good cave and etch it into stone.

Does it need to withstand fire or the elements? Does it need to survive burial underground or underwater?

I actually think there’s two facets at play here. There’s the first dimension, the durability of the medium itself against the environment, which is what you’re asking about. The second dimension is redundancy. It’s all well and good if you invest in aluminum but something heavy gets dropped on your plate and the singular copy is damaged beyond recovery. Worth considering that if this information is important enough to etch in metal, you should make several copies across a few different storage mediums in a handful of physical locations. A safe deposit box may not be a bad idea, for example.

Cryptosteel if kept in a fireproof container should easily last past 200 years.

I recall seeing a video a few years ago about a storage medium that does precisely this, stored data in the position of the metal ion of a perovskite. Although I can’t find the video anymore.