I'm having this issue as well, and none of the proposed solutions fix it for me.

I'm encountering this issue as well (Arch Linux), but to reproduce it here are the steps I take

1. open inkscape from start menu (inkscape needs to be already running & not have another document open)
2. open any svg file
3. crash occurs

Here's my backtrace, however it's roughly the same as Ellie's (minus some missing names)

 0# Inkscape::Application::crash_handler(int) in /usr/bin/../lib/inkscape/libinkscape_base.so.1.4.2.0
 1# 0x000000000003E540 in /usr/lib/libc.so.6
 2# InkscapeApplication::on_activate() in /usr/bin/../lib/inkscape/libinkscape_base.so.1.4.2.0
 3# Glib::SignalProxyNormal::slot0_void_callback(_GObject*, void*) in /usr/lib/libglibmm-2.4.so.1
 4# g_closure_invoke in /usr/bin/../lib/inkscape/../libgobject-2.0.so.0
 5# 0x0000000000031097 in /usr/bin/../lib/inkscape/../libgobject-2.0.so.0
 6# 0x0000000000032B0F in /usr/bin/../lib/inkscape/../libgobject-2.0.so.0
 7# g_signal_emit_valist in /usr/bin/../lib/inkscape/../libgobject-2.0.so.0
 8# g_signal_emit in /usr/bin/../lib/inkscape/../libgobject-2.0.so.0
 9# g_application_activate in /usr/bin/../lib/inkscape/../libgio-2.0.so.0
10# 0x00000000000E44B1 in /usr/bin/../lib/inkscape/../libgio-2.0.so.0
11# g_application_run in /usr/bin/../lib/inkscape/../libgio-2.0.so.0
12# main in /usr/bin/inkscape
13# 0x0000000000027675 in /usr/lib/libc.so.6
14# __libc_start_main in /usr/lib/libc.so.6
15# _start in /usr/bin/inkscape

                  Compile  (Run)
GLib version:     2.86.0
GTK version:      3.24.51 (3.24.51)
glibmm version:   2.66.8
gtkmm version:    3.24.10
libxml2 version:  2.15.0
libxslt version:  1.1.43
Cairo version:    1.18.4 (1.18.4)
Pango version:    1.57.0 (1.57.0)
HarfBuzz version: 12.1.0 (12.1.0)

OS version:       Arch Linux

I can provide a coredump if that would help

however, looking at the coredump in gdb, the problematic line seems to be: https://gitlab.com/inkscape/inkscape/-/blob/4dba481fe898c6317696d50b109f5aed8f269c19/src/inkscape-application.cpp#L1117

here is the backtrace that gdb prints:

#0  0x00007fefc4e4895d in Inkscape::UI::Dialog::StartScreen::get_document (this=0x0)
    at /usr/src/debug/inkscape/inkscape/src/ui/dialog/startup.h:52
#1  InkscapeApplication::on_activate (this=0x7ffdb7e8fde0) at /usr/src/debug/inkscape/inkscape/src/inkscape-application.cpp:1117
#2  0x00007fefc384f5d5 in sigc::slot0::operator() (this=0x56451233be48) at /usr/include/sigc++-2.0/sigc++/functors/slot.h:540
#3  Glib::SignalProxyNormal::slot0_void_callback (self=, data=0x56451233be40) at ../glibmm/glib/glibmm/signalproxy.cc:103
#8  0x00007fefc3702e44 in 
    (instance=instance@entry=0x5645122f5c10, signal_id=, detail=detail@entry=0) at ../glib/gobject/gsignal.c:3598
    #4  0x00007fefc36e197c in g_closure_invoke
    (closure=0x56451233bed0, return_value=0x0, n_param_values=1, param_values=0x7ffdb7e8f880, invocation_hint=0x7ffdb7e8f7d0)
    at ../glib/gobject/gclosure.c:916
    #5  0x00007fefc3701097 in signal_emit_unlocked_R
    (node=node@entry=0x7ffdb7e8f990, detail=detail@entry=0, instance=instance@entry=0x5645122f5c10, emission_return=emission_return@entry=0x0, instance_and_params=instance_and_params@entry=0x7ffdb7e8f880) at ../glib/gobject/gsignal.c:3976
    #6  0x00007fefc3702b0f in signal_emit_valist_unlocked
    (instance=instance@entry=0x5645122f5c10, signal_id=signal_id@entry=8, detail=detail@entry=0, var_args=var_args@entry=0x7ffdb7e8faf0)
    at ../glib/gobject/gsignal.c:3535
    #7  0x00007fefc3702d89 in g_signal_emit_valist (instance=0x5645122f5c10, signal_id=8, detail=0, var_args=var_args@entry=0x7ffdb7e8faf0)
    at ../glib/gobject/gsignal.c:3278
#9  0x00007fefc150ebc0 in g_application_activate (application=0x5645122f5c10 [gtkmm__GtkApplication]) at ../glib/gio/gapplication.c:2471
#10 g_application_activate (application=0x5645122f5c10 [gtkmm__GtkApplication]) at ../glib/gio/gapplication.c:2457
#11 0x00007fefc15124b1 in g_application_real_local_command_line
    (application=0x5645122f5c10 [gtkmm__GtkApplication], arguments=0x7ffdb7e8fc78, exit_status=0x7ffdb7e8fc74)
    at ../glib/gio/gapplication.c:1201
#12 0x00007fefc1512665 in g_application_run
    (application=0x5645122f5c10 [gtkmm__GtkApplication], argc=, argv=) at ../glib/gio/gapplication.c:2710
#13 0x00005644f5ba4d7a in main (argc=, argv=0x564512186310) at /usr/include/glibmm-2.4/glibmm/refptr.h:405

however, Inkscape::UI::Dialog::StartScreen::get_document() seems to no longer be present in master and is instead only present in the 1.4.x branch, and master new uses InkscapeApplication::document_new which has different logic, so I think that will fix it?

unsure why InkscapeApplication::on_activate() is being called rather than InkscapeApplication::on_open() though, as it's being opened by double clicking on the file, which according to the docs should instead cause it to call InkscapeApplication::on_open(). I've also checked, and I can reproduce it by calling inkscape [filename].

debug logs don't really reveal anything useful, but I didn't look too hard