Payment via digital gift cards sold on Amazon, e.g. Mullvad

Granted, this would probably be a very miniscule amount of their users.

That's not how businesses process payment. Any responsible finance department will call a hard no on that. (And from a consumer side, asking to pay with a gift card is usually a huge red flag that a scam is incoming)

I believe they mean a gift card for their service, as in they should offer gift cards. Not send us $50 worth of Google Play gift cards.

https://www.amazon.com/Mullvad-VPN-Devices-Protect-Security/...

Yep

This Valentine's Day, give someone the true gift of love, a search.