@phoenixci Was this part of the Project Stream test? Or is it actually stated for Stadia? If it was part of the Project Stream test, you need to claim it on Uplay to claim the digital copy.
If you're actually getting a code for Stadia, then try purchasing the game, and when you're at the part to enter payment information, change the payment method and you should see 'Redeem Code' option. I actually never had a code to redeem before, so can't test it myself, but this is the only place I can find to enter code. Can you try and see if it works? I'm actually curious myself.
Just tried to change payment method, was only offered to select a different credit card or a bank account, no redeem option
So nearly two years later, has this been resolved? I have the same issues with Stadia codes from Ubisoft