thank you for your query. Unfortunately, the person who runs the automated nightly builds has not set them up to produce the no graphics server version. However, you can compile it from source on Linux - just pull from the master branch on my Github repository
and compile using the simgraph0.cc (have a look at the makefile to see what options to select). Some information on compiling, although some of it is specific to Windows, can be found in this
thread, which covers certain dependencies and libraries that you will need to compile Simutrans-Experimental.
Please note that, with the current version of Simutrans-Experimental (9.5), you will not be able to join a game hosted on a Linux server from a Windows client or vice versa (or, indeed, any combination of client/server compiled in different architectures). This is a known bug and work is underway to fix it for the next release, 9.6.
Thank you for your interest in running a Simutrans-Experimental server!