How about encoding it into the DNA of very common animals, e.g. flies and cockroaches? The DNA is constantly being renewed in every generation, and there’s junk data that can be used to hold information. Hmm maybe we should start looking for messages in junk DNA.
The OP talked about preserving basic knowledge (“so that even in a mass die off we don’t lose the secret of concrete or gears or stuff”). Reading information encoded in DNA requires a very advanced level of technology, so in that case, presumably there has not been a mass die-off or a collapse of civilization. The Rosetta Disk, on the other hand, can be read visually. The unaided eye can read some of the information, although you do need an optical microscope to read the rest.
And the size of the writing shrinks smoothly, so being able to read the first part with the naked eye intrinsically tells you that there’s more hidden in the parts that are too small to read.