I am planning on travelling from Russia to Ukraine in
2017 via train and was curious if taking a direct train was still an option. I am aware of the Belarussian route but would prefer to not deal with the paperwork.
If you're Russian:
There is no problem to take a train right now, from Kiev to Moscow and vise versa. The problem is to get an ukranian visa, espesially for a men with suitable age for being in army. However, a friend of mine got a working trip to Kiev this year, so the political situation here is bad, but the transport connections still are available, if you are using the surface transport, the flights still cannot be made.
Still, the valid visa does not guarantee the successfull entrance, because of the political situation.
If you're resident of any other country you probably never face any troubles if your documents are valid, yet another border control.
There are a lot of trains between Moscow and Kiev, you can check them Russian Railways Passenger Information (if the link out of date, try their home page). I didn't hear about real problems vith visas or border-crossing between the Ukrain and Russia, we are just annoyed about the fact we now need to apply for visa, but I can believe it could be some things with getting visa.