By August 2016, the company had received at least US$7 million in angel investments from venture capital firms, including Peter Thiel's Founders Fund, Propel Venture Partners, Pantera Capital, Foundation Capital and the Digital Currency Group.[49]
My understanding is that Fennec only removes Mozilla's telemetry, whereas IronFox (forked from the discontinued Mull) is that plus patches to further harden the browser.
IronFox is available through F-Droid via the project's own repository, but is recommended to install through Accrescent, which you can learn more about here.