This is what I get. The initial errors (before the fatal unhandled exception) happen on launch. I have uninstalled and reinstalled PT9 a couple of times, once blowing away the ~/.local/share/Paratext90 folder, without change.
Mozilla Roots Importer - version 3.2.8.0
Download and import trusted root certificates from Mozilla’s MXR.
Copyright 2002, 2003 Motus Technologies. Copyright 2004-2008 Novell. BSD licensed.
Importing certificates into user store…
Import process completed.
(1,2): warning CS0105: The using directive for `System’ appeared previously in this namespace
Checking for ParatextProjects.
Apport Ignore file doesn’t need updating.
Updating EncConverts Registry Keys
Writing silencconverters40key key
SLT Resources already Installed.
(Paratext:6994): GLib-GObject-WARNING **: 17:02:11.358: invalid (NULL) pointer instance
(Paratext:6994): GLib-GObject-CRITICAL **: 17:02:11.358: g_signal_handler_disconnect: assertion ‘G_TYPE_CHECK_INSTANCE (instance)’ failed
(Paratext:6994): Gdk-CRITICAL **: 17:02:11.358: gdk_frame_clock_end_updating: assertion ‘GDK_IS_FRAME_CLOCK (frame_clock)’ failed
(Paratext:6994): GLib-GObject-WARNING **: 17:02:11.359: …/…/…/…/gobject/gsignal.c:2641: instance ‘0x7f93f1c9d380’ has no handler with id ‘853’
(Paratext:6994): GLib-GObject-WARNING **: 17:02:11.377: invalid (NULL) pointer instance
(Paratext:6994): GLib-GObject-CRITICAL **: 17:02:11.377: g_signal_handler_disconnect: assertion ‘G_TYPE_CHECK_INSTANCE (instance)’ failed
(Paratext:6994): Gdk-CRITICAL **: 17:02:11.377: gdk_frame_clock_end_updating: assertion ‘GDK_IS_FRAME_CLOCK (frame_clock)’ failed
(Paratext:6994): GLib-GObject-WARNING **: 17:02:11.377: …/…/…/…/gobject/gsignal.c:2641: instance ‘0x7f93f1c9d490’ has no handler with id ‘861’
(Paratext:6994): GLib-CRITICAL **: 17:02:12.187: Source ID 87 was not found when attempting to remove it
(Paratext:6994): GLib-CRITICAL **: 17:02:12.188: Source ID 86 was not found when attempting to remove it
(Paratext:6994): GLib-CRITICAL **: 17:02:12.188: Source ID 85 was not found when attempting to remove it
(Paratext:6994): GLib-CRITICAL **: 17:02:12.188: Source ID 88 was not found when attempting to remove it
(Paratext:6994): Gtk-CRITICAL **: 17:02:12.356: gtk_window_resize: assertion ‘height > 0’ failed
(Paratext:6994): Gtk-CRITICAL **: 17:02:12.356: gtk_window_resize: assertion ‘height > 0’ failed
(Paratext:6994): Gtk-CRITICAL **: 17:02:12.356: gtk_window_resize: assertion ‘height > 0’ failed
(Paratext:6994): Gtk-CRITICAL **: 17:02:12.357: gtk_window_resize: assertion ‘height > 0’ failed
(Paratext:6994): Gtk-CRITICAL **: 17:02:12.357: gtk_window_resize: assertion ‘height > 0’ failed
No LSB modules are available.
(Paratext:6994): GLib-GObject-WARNING **: 17:03:06.509: invalid (NULL) pointer instance
(Paratext:6994): GLib-GObject-CRITICAL **: 17:03:06.509: g_signal_handler_disconnect: assertion ‘G_TYPE_CHECK_INSTANCE (instance)’ failed
(Paratext:6994): Gdk-CRITICAL **: 17:03:06.509: gdk_frame_clock_end_updating: assertion ‘GDK_IS_FRAME_CLOCK (frame_clock)’ failed
(Paratext:6994): GLib-GObject-WARNING **: 17:03:06.509: …/…/…/…/gobject/gsignal.c:2641: instance ‘0x7f93f1c9dc00’ has no handler with id ‘1809’
(Paratext:6994): GLib-GObject-WARNING **: 17:03:06.518: invalid (NULL) pointer instance
(Paratext:6994): GLib-GObject-CRITICAL **: 17:03:06.518: g_signal_handler_disconnect: assertion ‘G_TYPE_CHECK_INSTANCE (instance)’ failed
(Paratext:6994): Gdk-CRITICAL **: 17:03:06.518: gdk_frame_clock_end_updating: assertion ‘GDK_IS_FRAME_CLOCK (frame_clock)’ failed
(Paratext:6994): GLib-GObject-WARNING **: 17:03:06.518: …/…/…/…/gobject/gsignal.c:2641: instance ‘0x7f93f1c9daf0’ has no handler with id ‘1811’
[ERROR] FATAL UNHANDLED EXCEPTION: System.ObjectDisposedException: Cannot write to a closed TextWriter.
at System.IO.StreamWriter.Flush (System.Boolean flushStream, System.Boolean flushEncoder) [0x0000b] in <8f2c484307284b51944a1a13a14c0266>:0
at System.IO.StreamWriter.Write (System.Char[] buffer, System.Int32 index, System.Int32 count) [0x0008a] in <8f2c484307284b51944a1a13a14c0266>:0
at System.IO.TextWriter.WriteLine (System.String value) [0x00083] in <8f2c484307284b51944a1a13a14c0266>:0
at System.IO.TextWriter.WriteLine (System.String format, System.Object arg0) [0x0000e] in <8f2c484307284b51944a1a13a14c0266>:0
at PtxUtils.UI.FlushOnCrashLogTraceListener+c__AnonStorey0.<>m__0 () [0x0009a] in /home/build/paratext-geckofx-linux-9.0/PtxUtils.UI/FlushOnCrashLogTraceListener.cs:56
at PtxUtils.UI.FlushOnCrashLogTraceListener+c__AnonStorey0.<>m__1 () [0x00000] in /home/build/paratext-geckofx-linux-9.0/PtxUtils.UI/FlushOnCrashLogTraceListener.cs:63
at System.Threading.ThreadHelper.ThreadStart_Context (System.Object state) [0x00017] in <8f2c484307284b51944a1a13a14c0266>:0
at System.Threading.ExecutionContext.RunInternal (System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, System.Object state, System.Boolean preserveSyncCtx) [0x0008d] in <8f2c484307284b51944a1a13a14c0266>:0
at System.Threading.ExecutionContext.Run (System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, System.Object state, System.Boolean preserveSyncCtx) [0x00000] in <8f2c484307284b51944a1a13a14c0266>:0
at System.Threading.ExecutionContext.Run (System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, System.Object state) [0x00031] in <8f2c484307284b51944a1a13a14c0266>:0
at System.Threading.ThreadHelper.ThreadStart () [0x0000b] in <8f2c484307284b51944a1a13a14c0266>:0