Any sources please?

I have this https://ecosia.helpscoutdocs.com/article/377-ip-addresses

When communicating your searches to Bing to provide you with results, we never communicate your IP address together with your search queries.

And this : https://www.ecosia.org/privacy

For example, when searching for “tree” on Ecosia we forward the following information to our partner, Bing: IP address (to a separate fraud detection server, so your search term and IP address are never sent to the same server), meta-data on your device that is necessary for the result like screen size, search term, and some settings like your country and language setting.

If you choose to enable “personalised search”, Ecosia sets a Bing-specific “customer ID” parameter to improve the quality of your search results. You can also choose to enable this feature by modifying your user settings.

The search request and IP are sent to separate servers and with different goals.

Mot likely the IP is sent to Bing to detect if it's bot. That way Ecosia can know when to send a captcha.

And the search request is sent by Ecosia without the IP or identifying informations.