The Fed has had a wire service (Fedwire) for banks, allowing them to transfer their balances on the Fed’s balance sheet to another bank during settlement, since before the dollar moved off the gold standard. It was initially done with literal telegraphs - not sure at what point it became digital.

It obviously has no pseudo anonymity, is literally the least democratized banking system in existence, and is subject to the government’s whims in a whole host of ways. But it is a digital ledger of massive sums of real dollars (the banks can ask for it in cash if need be), and you couldn’t really steal the money even if you managed to create an unauthorized transfer on some bank’s master account.