The simple answer is no.
The medium answer is that we used to have an exploit which could get access to Sky Go in a similar way to iPlayer, but for the time being that is null and void.
The detailed answer is that we do not have write access to the video buffer and audio output stream, and the processing and memory capacity of the HD- or HDR-FOX is somewhat limited, so without an Internet stream specifically tailored to be compatible with the dedicated hardware functionality (and using the same access mechanisms) it will be impossible to adapt open source code to do it.