Thread 1 "osgearth_viewer" received signal SIGSEGV, Segmentation fault.
0x00007ffff0f5e831 in OpenThreads::Thread::setProcessorAffinity(OpenThreads::Affinity const&) ()
I suppose that it has soemthing to to with the different versions of libOpenThreads on the system. OSG 3.5.9 compiles and uses libOpenThreads.so.21, while Ubuntu16.04 libOpenThreads.so.20.
So I recompiled osgEarth 2.9 with OSG 3.5.3 (which uses libOpenThreads.so.20) and it resolved the issue. At least for now ;)