I suspect the answer to this is "no" based on everything I've seen and looked up here, but just in case I'm missing something- if a player does not have an explicitly listed port (be it stable or unstable), it is not rockboxable, yes?
Bought a "Dansrue" player (it managed to become popular on Amazon, which I now realize was a terrible metric to base my own purchase on) and it's already such a lousy device that I'm willing to take chances with it. I have no idea if it would hypothetically even be rockboxable based on hardware, but it's never even come up on these forums that I've been able to find, so I don't even know that part.