I edited my post after re-reading your comments and looking at the keycap colours.

If the box promises k6 compatibility (unlike the store listings for each of the ITA-ISO sets) then you could ask Keychron for a partial refund or a store credit but they’re unlikely to process a full refund even if you offered to pay for shipping.

You might be able to convince them to credit the amount towards a keycap set that does have full compatibility