It's not available for consumers yet, and there are only 40 or so banks currently on the network.

Never seen an online shop accept that, nor do I know if it's open to UK citizens. But thanks

In the UK, you have Single European Payment Area payments. (Despite Brexit, the UK chose to stay within the SEPA zone.) The US didn't have a bank-level national service for consumer to consumer payments until FedNow. Just PayPal, Venmo, etc., which are second-tier services, which becomes an issue when they break.

Still better than cutting off most of the world. PayPal have their problems but neither a US-only nor an EU-only system is an improvement.