For everyone STILL having issues after following Diego Dotta's 6 step plan - I did too - I found the next solution for you.

Change the 'Memory Allocation' from [Default] to something else. I did 128MB*. When I did that, it worked.

I believe it's the same error as leaving the 'Region' as [Default]. Leaving anything as [Default] causes issues.

Other notes:

Picking a Region: I found which region the rest of my Firebase Project was set to by going to the Project Settings in the Cloud Console. It'll be next to: 'Default GCP resource location'. Use that.
Don't forget to reload the boilerplate code (green button, top right) whenever you change any settings - the code doesn't change dynamically.
Very strangely, when I first checked my package.json file, it was completely empty haha - regardless, we all still love FlutterFlow and this community is great👍

*I chose 128MB because it was the first number I saw. I don't know what it should be, but it'll obviously depend on your function.

Building Something - try this and let us know if it works for you.

Error deploying cloud functions on FF