RDM doesn't run with mono installed

I've worked on this quite a bit to no avail so far.
I am able to reproduce this issue even with a simple hello world application.
I've opened an issue with mono to try to clear things up so it's a waiting game for the moment.

This seems to be resolved in 2020.2.1.0

Really?
Glag to know but the fix was not on our end.

Heh, seems to be. You should be able to test in your Manjaro VM to get the latest mono.

My vm updated to mono 6.4.0.192-2 but it still doesn't work for me.

Hmm, so Manjaro will lag a bit on updates. I've currently got

$ pacman -Qe | grep mono
mono 6.8.0.123-1

Hi, i had this problem too but WITHOUT mono installed.

system: Ubuntu 20.04 (without snapd)

~$ remotedesktopmanager.free 

Unhandled Exception:
System.TypeInitializationException: The type initializer for 'GLib.Marshaller' threw an exception. ---> System.TypeInitializationException: The type initializer for 'Sys' threw an exception. ---> System.DllNotFoundException: /usr/lib/../lib/libmono-native.so assembly:<unknown assembly> type:<unknown type> member:(null)
  at (wrapper managed-to-native) Interop+Sys.LChflagsCanSetHiddenFlag()
  at Interop+Sys..cctor () [0x00000] in <c453bf849bb84e719dbec0475e99db95>:0 
   --- End of inner exception stack trace ---
  at System.IO.FileSystem.FileExists (System.ReadOnlySpan`1[T] fullPath, System.Int32 fileType, Interop+ErrorInfo& errorInfo) [0x00007] in <c453bf849bb84e719dbec0475e99db95>:0 
  at System.IO.FileSystem.FileExists (System.ReadOnlySpan`1[T] fullPath) [0x00006] in <c453bf849bb84e719dbec0475e99db95>:0 
  at System.IO.File.Exists (System.String path) [0x00043] in <c453bf849bb84e719dbec0475e99db95>:0 
  at System.TimeZoneInfo.TryLoadTzFile (System.String tzFilePath, System.Byte[]& rawData, System.String& id) [0x00000] in <c453bf849bb84e719dbec0475e99db95>:0 
  at System.TimeZoneInfo.TryGetLocalTzFile (System.Byte[]& rawData, System.String& id) [0x0000f] in <c453bf849bb84e719dbec0475e99db95>:0 
  at System.TimeZoneInfo.GetLocalTimeZoneFromTzFile () [0x00000] in <c453bf849bb84e719dbec0475e99db95>:0 
  at System.TimeZoneInfo.GetLocalTimeZone (System.TimeZoneInfo+CachedData cachedData) [0x00000] in <c453bf849bb84e719dbec0475e99db95>:0 
  at System.TimeZoneInfo+CachedData.CreateLocal () [0x00018] in <c453bf849bb84e719dbec0475e99db95>:0 
  at System.TimeZoneInfo+CachedData.get_Local () [0x0000c] in <c453bf849bb84e719dbec0475e99db95>:0 
  at System.TimeZoneInfo.get_Local () [0x00000] in <c453bf849bb84e719dbec0475e99db95>:0 
  at System.CurrentSystemTimeZone..ctor () [0x00011] in <c453bf849bb84e719dbec0475e99db95>:0 
  at System.TimeZone.get_CurrentTimeZone () [0x00024] in <c453bf849bb84e719dbec0475e99db95>:0 
  at GLib.Marshaller..cctor () [0x00096] in <5b0dd59206734c9f99b9f9b329cdd118>:0 
   --- End of inner exception stack trace ---
  at GLib.Global.set_ProgramName (System.String value) [0x00000] in <5b0dd59206734c9f99b9f9b329cdd118>:0 
  at Gtk.Application.SetPrgname () [0x00015] in <1bdf72322a644cc3917a854c8dfd1be8>:0 
  at Gtk.Application.Init () [0x00000] in <1bdf72322a644cc3917a854c8dfd1be8>:0 
  at Devolutions.RemoteDesktopManager.Program.Main (System.String[] args) [0x00000] in <03bd1ac7bedf44a4bef05e3c51491e10>:0 
[ERROR] FATAL UNHANDLED EXCEPTION: System.TypeInitializationException: The type initializer for 'GLib.Marshaller' threw an exception. ---> System.TypeInitializationException: The type initializer for 'Sys' threw an exception. ---> System.DllNotFoundException: /usr/lib/../lib/libmono-native.so assembly:<unknown assembly> type:<unknown type> member:(null)
  at (wrapper managed-to-native) Interop+Sys.LChflagsCanSetHiddenFlag()
  at Interop+Sys..cctor () [0x00000] in <c453bf849bb84e719dbec0475e99db95>:0 
   --- End of inner exception stack trace ---
  at System.IO.FileSystem.FileExists (System.ReadOnlySpan`1[T] fullPath, System.Int32 fileType, Interop+ErrorInfo& errorInfo) [0x00007] in <c453bf849bb84e719dbec0475e99db95>:0 
  at System.IO.FileSystem.FileExists (System.ReadOnlySpan`1[T] fullPath) [0x00006] in <c453bf849bb84e719dbec0475e99db95>:0 
  at System.IO.File.Exists (System.String path) [0x00043] in <c453bf849bb84e719dbec0475e99db95>:0 
  at System.TimeZoneInfo.TryLoadTzFile (System.String tzFilePath, System.Byte[]& rawData, System.String& id) [0x00000] in <c453bf849bb84e719dbec0475e99db95>:0 
  at System.TimeZoneInfo.TryGetLocalTzFile (System.Byte[]& rawData, System.String& id) [0x0000f] in <c453bf849bb84e719dbec0475e99db95>:0 
  at System.TimeZoneInfo.GetLocalTimeZoneFromTzFile () [0x00000] in <c453bf849bb84e719dbec0475e99db95>:0 
  at System.TimeZoneInfo.GetLocalTimeZone (System.TimeZoneInfo+CachedData cachedData) [0x00000] in <c453bf849bb84e719dbec0475e99db95>:0 
  at System.TimeZoneInfo+CachedData.CreateLocal () [0x00018] in <c453bf849bb84e719dbec0475e99db95>:0 
  at System.TimeZoneInfo+CachedData.get_Local () [0x0000c] in <c453bf849bb84e719dbec0475e99db95>:0 
  at System.TimeZoneInfo.get_Local () [0x00000] in <c453bf849bb84e719dbec0475e99db95>:0 
  at System.CurrentSystemTimeZone..ctor () [0x00011] in <c453bf849bb84e719dbec0475e99db95>:0 
  at System.TimeZone.get_CurrentTimeZone () [0x00024] in <c453bf849bb84e719dbec0475e99db95>:0 
  at GLib.Marshaller..cctor () [0x00096] in <5b0dd59206734c9f99b9f9b329cdd118>:0 
   --- End of inner exception stack trace ---
  at GLib.Global.set_ProgramName (System.String value) [0x00000] in <5b0dd59206734c9f99b9f9b329cdd118>:0 
  at Gtk.Application.SetPrgname () [0x00015] in <1bdf72322a644cc3917a854c8dfd1be8>:0 
  at Gtk.Application.Init () [0x00000] in <1bdf72322a644cc3917a854c8dfd1be8>:0 
  at Devolutions.RemoteDesktopManager.Program.Main (System.String[] args) [0x00000] in <03bd1ac7bedf44a4bef05e3c51491e10>:0 

the problem was that mono WAS NOT installed

~$ mono --version

Command «mono» not found, can be installed with:

sudo apt install mono-runtime

now, a while ago, I installed Pinta from gnome-software, then when I noticed that it installed mono system-wide, I immediately uninstalled it and use the flatpak version. For some reason this left me with a broken install where the binary was removed but some mono directories weren't, and this prevented me to install it again: apt would fail saying that /usr/lib/mono/ and /etc/mono/ weren't empty. So i deleted those two directories and now RDM works fine!

Hi,

Glad you could work this out.
Indeed, if the libs are present, even if mono is not installed, the mono embedded in RDM will try to use theme.
Which is ironic as we embedded the mono framework in RDM so it doesn't need to look for them.