I've created a detailed thread here: https://forums.freenas.org/index.php?threads/sonarr-installation.45969/

To recap:

I'm running FreeNAS-9.10-MASTER-201608240406 (0e8142f)
I've setup a standard jail and installed mono using pkg


root@Downloads:/usr/local/sonarr/logs # mono -V
Mono JIT compiler version 4.4.2 (Stable 4.4.2.11/f72fe45 Tue Aug 16 01:55:53 UTC 2016)
Copyright (C) 2002-2014 Novell, Inc, Xamarin Inc and Contributors. www.mono-project.com
TLS: __thread
SIGSEGV: altstack
Notification: kqueue
Architecture: amd64
Disabled: none
Misc: softdebug
LLVM: supported, not enabled.
GC: sgen



When I attempt to start NzbDrone (aka Sonarr)

root@sonarr_1:/usr/local/share/sonarr # mono --debug NzbDrone.exe

=================================================================
Got a SIGSEGV while executing native code. This usually indicates
a fatal error in the mono runtime or one of the native libraries
used by your application.
=================================================================


When I try to compile and install mono using ports, here is an excerpt:

if test -w /usr/ports/lang/mono/work/mono-4.4.2/mcs; then :; else chmod -R +w /usr/ports/lang/mono/work/mono-4.4.2/mcs; fi
cd /usr/ports/lang/mono/work/mono-4.4.2/mcs && gmake --no-print-directory -s NO_DIR_CHECK=1 PROFILES='binary_reference_assemblies net_4_x xbuild_12 xbuild_14 ' CC='cc' all-profiles
mkdir -p -- build/deps

=================================================================
Got a SIGSEGV while executing native code. This usually indicates
a fatal error in the mono runtime or one of the native libraries
used by your application.
=================================================================

gmake[7]: *** [build/profiles/basic.make:93: build/deps/basic-profile-check.exe] Abort trap
*** The compiler 'mcs' doesn't appear to be usable.
*** Trying the 'monolite' directory.

=================================================================
Got a SIGSEGV while executing native code. This usually indicates
a fatal error in the mono runtime or one of the native libraries
used by your application.
=================================================================

gmake[9]: *** [build/profiles/basic.make:93: build/deps/basic-profile-check.exe] Abort trap
*** The contents of your 'monolite' directory may be out-of-date
*** You may want to try 'make get-monolite-latest'
gmake[9]: *** [build/profiles/basic.make:80: do-profile-check-monolite] Error 1
gmake[8]: *** [build/profiles/basic.make:60: do-profile-check] Error 2
gmake[7]: *** [build/profiles/basic.make:88: do-profile-check-monolite] Error 2
gmake[6]: *** [build/profiles/basic.make:60: do-profile-check] Error 2
gmake[5]: *** [Makefile:49: profile-do--basic--all] Error 2
gmake[4]: *** [Makefile:45: profiles-do--all] Error 2
gmake[3]: *** [Makefile:543: all-local] Error 2
gmake[3]: Leaving directory '/usr/ports/lang/mono/work/mono-4.4.2/runtime'
gmake[2]: *** [Makefile:513: all-recursive] Error 1
gmake[2]: Leaving directory '/usr/ports/lang/mono/work/mono-4.4.2'
gmake[1]: *** [Makefile:442: all] Error 2
gmake[1]: Leaving directory '/usr/ports/lang/mono/work/mono-4.4.2'
===> Compilation failed unexpectedly.
Try to set MAKE_JOBS_UNSAFE=yes and rebuild before reporting the failure to
the maintainer.
*** Error code 1

Stop.
make: stopped in /usr/ports/lang/mono


For Reference:

Platform: http://www.supermicro.com/products/system/4U/6048/SSG-6048R-E1CR36N.cfm
CPU: 2 x Xeon E5-2623 v4
Memory: 12 x Samsung 16GB DDR4-2133 2Rx4 LP ECC REG RoHs (192GB Total)
SAS Controller(s): LSI 3008
Hard Drives: 36 x WD Red 8TB (9 x 4 in Z2)