Hmm, some interesting updates here. Firstly, here's the output from totem when run with "G_MESSAGES_DEBUG=all":

(totem:38425): GLib-GIO-DEBUG: 11:13:06.494: _g_io_module_get_default: Found default implementation dconf (DConfSettingsBackend) for ‘gsettings-backend’
(totem:38425): dconf-DEBUG: 11:13:06.495: watch_fast: "/org/gnome/Totem/" (establishing: 0, active: 0)
(totem:38425): dconf-DEBUG: 11:13:06.503: watch_established: "/org/gnome/Totem/" (establishing: 1)
(totem:38425): dconf-DEBUG: 11:13:06.530: watch_fast: "/org/gnome/desktop/interface/" (establishing: 0, active: 0)
(totem:38425): dconf-DEBUG: 11:13:06.530: watch_fast: "/org/gnome/desktop/peripherals/mouse/" (establishing: 0, active: 0)
(totem:38425): dconf-DEBUG: 11:13:06.530: watch_fast: "/org/gnome/desktop/sound/" (establishing: 0, active: 0)
(totem:38425): dconf-DEBUG: 11:13:06.531: watch_fast: "/org/gnome/desktop/privacy/" (establishing: 0, active: 0)
(totem:38425): dconf-DEBUG: 11:13:06.531: watch_fast: "/org/gnome/desktop/wm/preferences/" (establishing: 0, active: 0)
(totem:38425): dconf-DEBUG: 11:13:06.531: watch_fast: "/org/gnome/settings-daemon/plugins/xsettings/" (establishing: 0, active: 0)
(totem:38425): dconf-DEBUG: 11:13:06.531: watch_fast: "/org/gnome/desktop/a11y/" (establishing: 0, active: 0)
(totem:38425): dconf-DEBUG: 11:13:06.531: watch_fast: "/org/gnome/desktop/a11y/interface/" (establishing: 0, active: 0)
(totem:38425): dconf-DEBUG: 11:13:06.532: watch_established: "/org/gnome/desktop/interface/" (establishing: 1)
(totem:38425): dconf-DEBUG: 11:13:06.532: watch_established: "/org/gnome/desktop/peripherals/mouse/" (establishing: 1)
(totem:38425): dconf-DEBUG: 11:13:06.534: watch_established: "/org/gnome/desktop/sound/" (establishing: 1)
(totem:38425): dconf-DEBUG: 11:13:06.534: watch_established: "/org/gnome/desktop/privacy/" (establishing: 1)
(totem:38425): dconf-DEBUG: 11:13:06.534: watch_established: "/org/gnome/desktop/wm/preferences/" (establishing: 1)
(totem:38425): dconf-DEBUG: 11:13:06.535: watch_established: "/org/gnome/settings-daemon/plugins/xsettings/" (establishing: 1)
(totem:38425): dconf-DEBUG: 11:13:06.535: watch_established: "/org/gnome/desktop/a11y/" (establishing: 1)
(totem:38425): dconf-DEBUG: 11:13:06.535: watch_established: "/org/gnome/desktop/a11y/interface/" (establishing: 1)
(totem:38425): GLib-GIO-DEBUG: 11:13:06.678: _g_io_module_get_default: Found default implementation gvfs (GDaemonVfs) for ‘gio-vfs’
(totem:38425): GLib-DEBUG: 11:13:06.793: unsetenv() is not thread-safe and should not be used after threads are created
(totem:38425): Gtk-DEBUG: 11:13:06.793: Connecting to session manager
(totem:38425): Handy-DEBUG: 11:13:06.797: Trying to initialize portal
(totem:38425): dconf-DEBUG: 11:13:07.282: watch_fast: "/org/gnome/Totem/" (establishing: 0, active: 1)
(totem:38425): dconf-DEBUG: 11:13:07.282: watch_fast: "/org/gnome/desktop/lockdown/" (establishing: 0, active: 0)
(totem:38425): dconf-DEBUG: 11:13:07.283: watch_established: "/org/gnome/desktop/lockdown/" (establishing: 1)
(totem:38425): dconf-DEBUG: 11:13:07.549: watch_fast: "/org/gnome/desktop/thumbnailers/" (establishing: 0, active: 0)
(totem:38425): dconf-DEBUG: 11:13:07.550: watch_established: "/org/gnome/desktop/thumbnailers/" (establishing: 1)
(totem:38425): GLib-GIO-DEBUG: 11:13:07.559: Failed to initialize portal (GNetworkMonitorPortal) for gio-network-monitor: Not using portals
(totem:38425): GLib-GIO-DEBUG: 11:13:07.569: _g_io_module_get_default: Found default implementation networkmanager (GNetworkMonitorNM) for ‘gio-network-monitor’
(totem:38425): dconf-DEBUG: 11:13:07.570: watch_fast: "/org/gnome/Totem/" (establishing: 0, active: 2)
(totem:38425): dconf-DEBUG: 11:13:07.570: unwatch_fast: "/org/gnome/Totem/" (active: 3, establishing: 0)
(totem:38425): GLib-GIO-DEBUG: 11:13:07.630: _g_io_module_get_default: Found default implementation gnutls (GTlsBackendGnutls) for ‘gio-tls-backend’
(totem:38425): dconf-DEBUG: 11:13:07.813: change_fast
(totem:38425): dconf-DEBUG: 11:13:07.815: watch_fast: "/org/gnome/Totem/" (establishing: 0, active: 2)
(totem:38425): dconf-DEBUG: 11:13:07.816: unwatch_fast: "/org/gnome/Totem/" (active: 3, establishing: 0)
(totem:38425): dconf-DEBUG: 11:13:07.816: watch_fast: "/org/gnome/Totem/" (establishing: 0, active: 2)
(totem:38425): dconf-DEBUG: 11:13:07.834: watch_fast: "/org/gnome/Totem/" (establishing: 0, active: 3)
(totem:38425): dconf-DEBUG: 11:13:07.862: watch_fast: "/org/gnome/desktop/lockdown/" (establishing: 0, active: 1)
(totem:38425): Totem-DEBUG: 11:13:08.657: TotemGrilo: Pausing videos thumbnailing
(totem:38425): Totem-DEBUG: 11:13:08.675: totem_playlist_add_one_mrl (): big_buck_bunny_720p_surround.mp4 (null) (null) (null) 0 false
(totem:38425): Totem-DEBUG: 11:13:08.719: Adding popup busy for reason opening file
(totem:38425): Totem-DEBUG: 11:13:08.721: emitting PlaybackStatus change
(totem:38425): Totem-DEBUG: 11:13:08.721: Not enabling offline save, as 'file:///home/dave/big_buck_bunny_720p_surround.mp4' already in $HOME, and native
(totem:38425): Totem-DEBUG: 11:13:08.723: TotemGrilo: Pausing videos thumbnailing
(totem:38425): Totem-DEBUG: 11:13:08.727: Removing popup busy for reason opening file
(totem:38425): Totem-DEBUG: 11:13:08.727: Will hide popup soon
(totem:38425): Totem-DEBUG: 11:13:08.728: emitting PlaybackStatus change
(totem:38425): Totem-DEBUG: 11:13:08.735: Removing popup busy for reason paused
(totem:38425): Totem-DEBUG: 11:13:08.735: Will hide popup soon
(totem:38425): Totem-DEBUG: 11:13:08.735: successfully acquired dbus name org.mpris.MediaPlayer2.totem
(totem:38425): Totem-DEBUG: 11:13:08.753: emitting PlaybackStatus change
(totem:38425): dconf-DEBUG: 11:13:11.427: unwatch_fast: "/org/gnome/Totem/" (active: 4, establishing: 0)
(totem:38425): dconf-DEBUG: 11:13:11.430: unwatch_fast: "/org/gnome/desktop/lockdown/" (active: 2, establishing: 0)
(totem:38425): dconf-DEBUG: 11:13:11.437: unwatch_fast: "/org/gnome/Totem/" (active: 3, establishing: 0)
(totem:38425): Totem-DEBUG: 11:13:11.482: Removing popup busy for reason buffering
(totem:38425): Totem-DEBUG: 11:13:11.482: Will hide popup soon
(totem:38425): dconf-DEBUG: 11:13:11.599: unwatch_fast: "/org/gnome/desktop/thumbnailers/" (active: 1, establishing: 0)

Secondly, the *first* time I ran totem, it additionally reported:

double free or corruption (out)
Aborted (core dumped)

Unfortunately, I wasn't capturing stderr at that point and no subsequent run reported the same crash. apport obviously popped up on that core dump and I opted to report the error, which can found under the following OOPS:

https://errors.ubuntu.com/oops/927e463e-c15b-11ec-8afa-fa163e993415

I should also note (anecdotally) that the source_totem.py hook in apport also reported an error in syslog:

Apr 21 11:12:33 miss-piggy update-notifier-crash[37540]: ERROR: hook /usr/share/apport/package-hooks/source_totem.py crashed:
Apr 21 11:12:33 miss-piggy update-notifier-crash[37540]: Traceback (most recent call last):
Apr 21 11:12:33 miss-piggy update-notifier-crash[37540]:   File "/usr/lib/python3/dist-packages/apport/report.py", line 228, in _run_hook
Apr 21 11:12:33 miss-piggy update-notifier-crash[37540]:     symb['add_info'](report, ui)
Apr 21 11:12:33 miss-piggy update-notifier-crash[37540]:   File "/usr/share/apport/package-hooks/source_totem.py", line 9, in add_info
Apr 21 11:12:33 miss-piggy update-notifier-crash[37540]:     response = ui.choice("How would you describe the issue?", ["The totem interface 
is not working correctly", "No sound is being played", "Some audio files or videos are not being played correctly"], False)
Apr 21 11:12:33 miss-piggy update-notifier-crash[37540]: AttributeError: 'NoneType' object has no attribute 'choice'

Running with "G_DEBUG=fatal_warnings" produced no differences to the prior runs (no additional messages, no crash, etc.)