Redeemable on the Shopback app. I was personally apprehensive being burnt by the Shopback app couple of times but was able to purchase the e-gift cards right within the app, without having to go to Doordash.
Cashback also appeared instantly on the app post purchase and was able to verify the egiftcards as credits on Doordash too.
Increased cashback expires 25 July as per link. Usual is 10%.
Doordash gift cards are currently sold out as of 16-Jul-2021. If you see it come back in stock again, please use the report link for moderator attention