I'd say Bitcoin is backed up by nothing, and it doesn't need to be backed by something.
It's a pure digital bearer instrument with no counterparty risk.
Computational proof-of-work makes transections on the timechain immutable/irreversible.
The idea that #Bitcoin needs to be backed by something comes from the fiat 🤡 world where each asset is someone else's liability.
There's also no yield on Bitcoin, it's the value of the monetary network which accrues.
The idea that money should be backed by something actually comes from the era of the gold standard, which was pretty much all of history before 1971.
Fiat money is literally defined as money that isn't backed by anything tangible.
However wrt Bitcoin, it is very much open to debate and your view of the role PoW takes is just as valid as mine.
And ofc Bitcoin has other unique qualities that make it more valuable than fiat, most obvious is the 21 million supply limit.
