BLACK20
Received the notification in the email, and not too much details yet (such as whether apply to both physical and digital cards, so, patience will eventually give one answers), other than the 20% off and that it starts at midnight. But it seems fairly self-explanatory. A quick note that I couldn't load any details except for the countdown in Opera browser (not sure if related to Tracking-/Ad-Blockers), but everything loads fine in Edge browser.
To search for participating restaurants: https://goodfoodgiftcard.com.au/Restaurants/Search
FAQs regarding the Good Food Gift Cards: https://goodfoodgiftcard.com.au/Faq
What kind of payment methods do you accept?
At Good Food Gift Card, we accept Mastercard, Visa, American Express and Diners. All payments are protected by SSL (Secure Sockets Layer) and Secure Data Encryption. All credit card payments are processed in real-time for your security and immediate peace of mind.
To avoid AmEx payment surcharge, just pay via PayPal.
UPDATE: 20% off applies to both physical and digital cards (exclude postage). Minimum spend $200.
Found the egift card version hard to use at some restaurants, claiming they didn't know how to use it. Would only buy for restaurants that you regularly go and they are familiar how to use it.