I have Unreal 4.26.1 compiled from source and working great when compiling a dedicated server and client, without Cesium assets added to the map.
I have also compiled Cesium from source and it works great within the editor, or when compiled to run as a standalone exe.
When I compile the dedicated server, and then the client, and then run the server, it comes up and waits for a connection, with no errors or warnings. When a client connects the server crashes. I can see red error text scroll by, and then the server log window closes. The server does not write the log to a file, it stops logging just until the crash. I will put video recording software on the log window and slow down the footage to read the screen and post the errors here.
In the mean time, has anyone tried to compile a dedicated server with the Cesium plugin? What has been your experience with multiple users?