Martin -
Are you installing a 7.80 or 7.93 robot on your Ubuntu 16 server? As the Unified Infrastructure Management Compatibility Matrix document specifies, 7.80 is not support on this Linux OS.
You will need to download the appropriate 7.93 install_Linux_23* package if you install using nimldr or the robot_rpm package if you install using the Linux native installer (rpm). The package needs to be downloaded into the local archive on your primary hub and then deployed to the primary hub. Once you have the appropriate 7.93 robot installation package installed on your primary hub, run the robot install again for your Ubuntu 16 server.
If you are attempting to install the 7.93 robot and it is failing, then I would recommend that you open a support case for this.
Hope this helps.