I was always annoyed by the non-existence of a wallet that can simply pay any QR code. Someone wants Monero, Litecoin, Zcash and I don't have it. But I have a lightning wallet, which has instant finality, so we can use a swap service for payment.
Instructions: go (on mobile, or desktop) to the page:
If you want, you can add to home screen and it will install as an app (PWA) on mobile. But for now use it from the browser, there will be changes, so you don't have to clear cache.
Click Scan QR Code and scan the payment code (I haven't tried Ethereum tokens yet, BTC, LTC and XMR work, ZEC should too).
If there's no amount in the QR code, the app will ask for it (in target currency), but the point is rather to pay QR codes on various terminals that already include the amount.
After creating a trade (note: the amount must be around $10 or more, otherwise Trocador API can't find the relevant trade route, as most exchanges have minimum amounts that they can swap, so it won't work for one flat white) a payment option will appear in your installed wallet (you can also copy the invoice or display a QR code). The list of recent trades is saved (locally in your browser). The server doesn't log anything - although Trocador might log, see privacy policy.
So the process: Scan (or paste) payment code, pay with lightning wallet, deal done. All support is handled by Trocador, in the trades list you'll find all info needed for the trade.
The algorithm for searching the exchange - rule out all D level KYC exchanges first (per trocador definition, but currently they don't have any anyway), cut out anything more expensive than 101% of the cheapest and then pick the one that is the fastest to complete the trade.
Don't be reckless, small amounts only, it might not work.