Personally I went to https://console.cloud.google.com since I already had some GCP projects. Then I searched for Gemini API Key. It brought me to https://console.cloud.google.com/agent-platform/studio/setti.... Then, there was a banner saying "Enable APIs to access full platform capabilities." Then, I did that, which took quite a while (minutes). Finally, I was able to see the way to create an API key.
The fact that there's two ways to get keys is also very confusing.