I've not been able to start gdm3 for quite a while now. I've tried upgrading to the latest nvidia driver in experimental (535.43.02-1) , and WaylandEnable=false in /etc/gdm3/daemon.conf
Swapping to the nouveau driver didn't seem to fix it, but then I removed the WaylandEnable=false and it started to work. I sadly have reasons to use the Nvidia drivers. systemd-coredump[101602]: Process 101572 (gnome-shell) of user 112 dumped core. Module libzstd.so.1 from deb libzstd-1.5.5+dfsg2-2.amd64 Module libudev.so.1 from deb systemd-255~rc3-2.amd64 Module libsystemd.so.0 from deb systemd-255~rc3-2.amd64 Stack trace of thread 101572: #0 0x00007fa966eced34 meta_display_get_x11_display (libmutter-12.so.0 + 0xced34) #1 0x00007fa966ef9aeb meta_cursor_sprite_xfixes_initable_init (libmutter-12.so.0 + 0xf9aeb) #2 0x00007fa9674923f3 g_initable_new_valist (libgio-2.0.so.0 + 0x7f3f3) #3 0x00007fa9674924dd g_initable_new (libgio-2.0.so.0 + 0x7f4dd) #4 0x00007fa966ef9e8a meta_cursor_sprite_xfixes_new (libmutter-12.so.0 + 0xf9e8a) #5 0x00007fa966efd69e ensure_xfixes_cursor (libmutter-12.so.0 + 0xfd69e) #6 0x00007fa966efd6fd meta_cursor_tracker_x11_get_sprite (libmutter-12.so.0 + 0xfd6fd) #7 0x00007fa966e8b05e meta_cursor_tracker_get_sprite (libmutter-12.so.0 + 0x8b05e) #8 0x00007fa96706640e ffi_call_unix64 (libffi.so.8 + 0x740e) #9 0x00007fa96706571d ffi_call_int (libffi.so.8 + 0x671d) #10 0x00007fa967065ef3 ffi_call (libffi.so.8 + 0x6ef3) #11 0x00007fa9671d46c7 _ZN3Gjs8Function6invokeEP9JSContextRKN2JS8CallArgsENS3_6HandleIP8JSObjectEEP11_GIArgument (libgjs.so.0 + 0x4c6c7) #12 0x00007fa9671d4f87 _ZN3Gjs8Function4callEP9JSContextjPN2JS5ValueE (libgjs.so.0 + 0x4cf87) #13 0x00007fa96437eb0e _Z12CallJSNativeP9JSContextPFbS0_jPN2JS5ValueEEN2js10CallReasonERKNS1_8CallArgsE (libmozjs-115.so.0 + 0x17eb0e) #14 0x00007fa964370860 InternalCall (libmozjs-115.so.0 + 0x170860) #15 0x00007fa96437e843 MaybeEnterInterpreterTrampoline (libmozjs-115.so.0 + 0x17e843) #16 0x00007fa964380c81 _ZN2js13ExecuteKernelEP9JSContextN2JS6HandleIP8JSScriptEENS3_IP8JSObjectEENS_16AbstractFramePtrENS2_13MutableHand leINS2_5ValueEEE (libmozjs-115.so.0 + 0x180c81) #17 0x00007fa9643e013d _ZN2js12ModuleObject7executeEP9JSContextN2JS6HandleIPS0_EE (libmozjs-115.so.0 + 0x1e013d) #18 0x00007fa9644c1deb InnerModuleEvaluation (libmozjs-115.so.0 + 0x2c1deb) #19 0x00007fa9644c21a3 _ZN2js14ModuleEvaluateEP9JSContextN2JS6HandleIPNS_12ModuleObjectEEENS2_13MutableHandleINS2_5ValueEEE (libmozjs-11 5.so.0 + 0x2c21a3) #20 0x00007fa96720ae08 _ZN17GjsContextPrivate11eval_moduleEPKcPhPP7_GError (libgjs.so.0 + 0x82e08) #21 0x00007fa96720b2e2 gjs_context_eval_module (libgjs.so.0 + 0x832e2) #22 0x00007fa96720b401 gjs_context_eval_module_file (libgjs.so.0 + 0x83401) #23 0x00007fa96761f7c9 n/a (libshell-12.so + 0x1f7c9) #24 0x00007fa966eaf048 meta_compositor_do_manage (libmutter-12.so.0 + 0xaf048) #25 0x00007fa966ece606 meta_display_new (libmutter-12.so.0 + 0xce606) #26 0x00007fa966ed9f60 meta_context_start (libmutter-12.so.0 + 0xd9f60) #27 0x000055ed5de2298e n/a (gnome-shell + 0x398e) #28 0x00007fa966c456ca __libc_start_call_main (libc.so.6 + 0x276ca) #29 0x00007fa966c45785 __libc_start_main_impl (libc.so.6 + 0x27785) #30 0x000055ed5de22c71 n/a (gnome-shell + 0x3c71)