I specifically mentioned the "little green men" because it was Russia's way to funnel an army into an independent country while claiming that they are just part of a local militia.
It's not a direct attack and worked out pretty much perfectly in 2014. It would absolutely be a way to continue the conflict, even within NATO countries. Though they need to create a rift within the population first to make such an uprising believable.
Moldova is already at this stage and the leaked plans from the start of the war actually had Transnistria next up on their list.
I don't think there is any dirt on Trump that could do actual damage at this point. His base hasn't dropped him after all the heinous things that have come out so far. They have zero morals.