Thanks for reminding me about Ecosia. I hadn't seen any of this, so I looked at their privacy policy and they actually refer to Mistral as if it is their exclusive provider:
LLM provider
We offer an AI-based chat service that allows you to have back and forth conversations on topics of your choice. If you use our chat service, queries will be sent to our model provider Mistral AI.
But then, much farther down, they mention OpenAI.
The provider we primarily use is Mistral AI... Ecosia may engage OpenAI as a backup service provider where Mistral is unavailable or a fallback is necessary to ensure continuity... You can find more information in OpenAI’s privacy policy. OpenAI will store your input and output data for 30 days for quality assurance purposes.