Detroit Red Wings
This is always the copout answer, but Trouba is from Rochester, Michigan. He might be open to sending him to the team he grew up watching. This was something that was apparently discussed during the summer as the Rangers looked to find a trade partner for the big defenseman, but he was unwilling to waive his then no-movement clause to make the trade happen.
Where the Rangers may not be so willing to make this trade is what they'd need to take back. Detroit isn't swimming in cap space, and there would probably have to be a few exchanges of bad deals to make this happen. Whether that is former Ranger Andrew Copp returning or perhaps the Rangers agreeing to take on Ben Chiarot's contract, the Rangers would have to take money back to make it work.
Steve Yzerman has always been a fan of big, physical defensemen, and getting Trouba to the Red Wings could be a fit that makes Detroit's organization feel more ready to push for the postseason once more. They've been on the outside looking in for the last eight seasons, and that is an organization that's coming off the longest-ever postseason streak in NHL history.