Buy British

I think someone else said the same, so those don't appear to be an option.

Visa appears to be the most common in the UK as far as I have seen. It is disappointing, but I guess it works for the banks etc kinda like the national grid for electricity.

I looked a little into open banking and Money Savings Expert say "Technically, banks share your information securely via technology called application programming interfaces (APIs). APIs simply allow two providers to 'talk' to each other and pass the information you've given permission to share, such as your bank balance and regular payments. " which doesn't sound like Visa or others are involved to me.

There's also https://www.openbanking.org.uk/what-is-open-banking/ which says much the same with no mention of Visa etc.

Banks do have systems to transfer money that doesn't involve Visa etc. It looks to me like open banking uses this or is a new system.

I had a look at Stripe also, this appears to be for businesses with customer's requiring to use debit or credit cards so that's ruled out!

Online banks: Starling bank uses MC but Revolut doesn't say what system they use with their cards.

There's Skrill, an e-wallet company. You can transfer in using open banking and can pay online without a card but I suspect the number of businesses that facilitate payment from them may be low. You can get a physical or virtual card, but that uses MC.

I found reference to a number of other e-wallet compnies but you'll have to do you're own research from here!

The king has cash

"Is there something I could get that’s widely accepted?"

Probably not if you're in a country that didn't skip over cards.

In China, for example, there's one protocol, the QR at the prodce stand or the hotel tell you where to send or receive money from, you check the details, enter the password, the transfer executes.

So if you move to country that's moved past cards, then ecommerce is running on mobile digital wallets or bank accounts(older digital wallets) directly that you can join.

"I don’t even get this, how is a QR code a payment method?"

You have a digital wallet like a bank account. Scanning a QR code tells you where to send or receive money, if everything looks correct, you enter your account password and the transfer executes.

"I assume those countries you’re talking about were just using cash up until the technology became available"

Depends on the country, but epayments were around before QR codes, bank account to bank account directly via different platforms.

"You don’t get charged to own a debit or credit card, unless..."

Unless you do, correct. You also don't have a bicycle...unless you do.