At some point, HomeDepot.com began selling third-party gift cards, and they are apparently processing these themselves (not outsourced to a third party processor). And so buying third-party gift cards might be a way to trigger things like AmEx Offers, portal bonuses, etc.
Direct Link to third-party gift cards on Homedepot.com (contains our affiliate link)
I don’t see many great brands there, but there are some that are semi interesting: BP gas, Grubhub, Disney, Delta. You can filter by brand to find the card you want.