GCP was the hardest to prepare for since the certification itself is very new and was also in Beta mode a while ago. If you look on their webpage for this exam, they seem to be providing a learning path, but it only points you to several external links and courses, a lot of which are paid. And hence, definitely not a single stop resource. There is this Coursera course which might serve as a single stop resource, but I did not try it as I was not willing to spend for it (didn't want to rush through the 7 day free trial either), but people willing to spend can try it out and let me and others know if it was useful.