[easyThrowaway]

The "whatever" part, in strict terms, would be information. Jury is still out whether that is a fundamental component of the universe or not: https://www.pbs.org/wgbh/nova/article/is-information-fundame...

[eru]

Well, thermodynamics is considered pretty fundamental, and the second law of thermodynamics is pretty much all about information. (But your link already touches that.)

People also interpret the 'unitarity' of quantum mechanics to mean that information is preserved.