ffmpeg is deployed everywhere, and old versions of ffmpeg are baked into a lot of devices.

If you have a device that does image, audio or video, libav and/or ffmpeg is likely somewhere in the stack. Your TV, camera, console or streaming device might use the software.

If you're using SaaS that does image, audio or video, they are likely using ffmpeg related software somewhere in their stack.

Same thing with apps, Android and iOS apps might use the libraries, as well as desktop apps.