Also Kindu has beautiful old Belgian buildings. See for example this picture I shot about half a year ago when in Kindu. The city also has a train station. And yes, the trains still operate. For $50 you have a first-class ticket to Lubumbashi. I checked the price last week at the station; I did not check the 'first-class'. For more info about Congos's railroad system please see this. The only problem is that the train arrives and leaves rather irregularly: maybe once or twice a month a train arrives at the station. In addition, it's very likely you get stuck for a few weeks during the trip because the trains have a tendency to break down.
Fig 6. Kindu's train station. If you look carefully in the back you see
cranes. The Congo river is there and it used to be a port. Now there
are piroques and carcasses of Belgian-time boats.
Fig 7. More train station.