Extraordinary System Monitor activity during slow startup of Etiona

During a startup last night I captured the syslog after an occasionally recurring burst of system
activity that even stalled the System Monitor for a minute or two:
Aug 6 20:05:40 george-ThinkPad-T420 systemd[1]: Starting Flush Journal to Persistent Storage...
...
Aug 6 20:06:42 george-ThinkPad-T420 dbus-daemon[1078]: [session uid=1000 pid=1078] Activating via systemd: service name='org.gnome.evolution.dataserver.Sources5' unit='evolution-source-registry.service' requested by ':1.66' (uid=1000 pid=1362 comm="/usr/lib/x86_64-linux-gnu/indicator-datetime/indic" label="unconfined")
Aug 6 20:06:42 george-ThinkPad-T420 dbus-daemon[1078]: [session uid=1000 pid=1078] Activation via systemd failed for unit 'evolution-source-registry.service': Unit evolution-source-registry.service not found.
Aug 6 20:06:42 george-ThinkPad-T420 dbus-daemon[822]: [system] Activating via systemd: service name='org.freedesktop.timedate1' unit='dbus-org.freedesktop.timedate1.service' requested by ':1.99' (uid=1000 pid=1362 comm="/usr/lib/x86_64-linux-gnu/indicator-datetime/indic" label="unconfined")
Aug 6 20:06:42 george-ThinkPad-T420 systemd[1]: Starting Time & Date Service...
Aug 6 20:06:42 george-ThinkPad-T420 dbus-daemon[822]: [system] Successfully activated service 'org.freedesktop.timedate1'
Aug 6 20:06:42 george-ThinkPad-T420 systemd[1]: Started Time & Date Service.
Aug 6 20:06:43 george-ThinkPad-T420 dbus-daemon[822]: [system] Activating service name='net.launchpad.backintime.serviceHelper' requested by ':1.102' (uid=1000 pid=1353 comm="python3 /usr/share/backintime/common/backintime.py" label="unconfined") (using servicehelper)
Aug 6 20:06:43 george-ThinkPad-T420 caja: [N-A] Caja-Actions Tracker 1.8.3 initializing...
Aug 6 20:06:44 george-ThinkPad-T420 ntpdate[1241]: adjust time server 91.189.91.157 offset -0.019216 sec
Aug 6 20:06:50 george-ThinkPad-T420 kernel: [ 179.782315] EXT4-fs (sdc3): mounted filesystem with ordered data mode. Opts: (null)
Aug 6 20:06:50 george-ThinkPad-T420 systemd[1]: Created slice system-clean\x2dmount\x2dpoint.slice.
Aug 6 20:06:50 george-ThinkPad-T420 systemd[1]: Started Clean the /media/george/b8a1ee74-96d2-407a-8d4e-98df997fcbe3 mount point.
Aug 6 20:06:50 george-ThinkPad-T420 udisksd[820]: Mounted /dev/sdc3 at /media/george/b8a1ee74-96d2-407a-8d4e-98df997fcbe3 on behalf of uid 1000
Aug 6 20:06:50 george-ThinkPad-T420 dbus-daemon[822]: [system] Successfully activated service 'net.launchpad.backintime.serviceHelper'
Aug 6 20:06:50 george-ThinkPad-T420 backintime (george/1): ERROR: Back In Time is not configured!
Aug 6 20:06:52 george-ThinkPad-T420 wpa_supplicant[839]: wlx00c0ca82ec36: CTRL-EVENT-SIGNAL-CHANGE above=1 signal=-54 noise=9999 txrate=65000
Aug 6 20:07:10 george-ThinkPad-T420 systemd[1]: dev-disk-by\x2duuid-67565b77\x2d4da7\x2d4b46\x2da159\x2db25ff8ce9b0d.device: Job dev-disk-by\x2duuid-67565b77\x2d4da7\x2d4b46\x2da159\x2db25ff8ce9b0d.device/start timed out.
Aug 6 20:07:10 george-ThinkPad-T420 systemd[1]: Timed out waiting for device dev-disk-by\x2duuid-67565b77\x2d4da7\x2d4b46\x2da159\x2db25ff8ce9b0d.device.
Aug 6 20:07:10 george-ThinkPad-T420 systemd[1]: Dependency failed for /dev/disk/by-uuid/67565b77-4da7-4b46-a159-b25ff8ce9b0d.
Aug 6 20:07:10 george-ThinkPad-T420 systemd[1]: dev-disk-by\x2duuid-67565b77\x2d4da7\x2d4b46\x2da159\x2db25ff8ce9b0d.swap: Job dev-disk-by\x2duuid-67565b77\x2d4da7\x2d4b46\x2da159\x2db25ff8ce9b0d.swap/start failed with result 'dependency'.
Aug 6 20:07:10 george-ThinkPad-T420 systemd[1]: Startup finished in 8.225s (kernel) + 3min 11.639s (userspace) = 3min 19.865s.
Aug 6 20:07:10 george-ThinkPad-T420 systemd[1]: dev-disk-by\x2duuid-67565b77\x2d4da7\x2d4b46\x2da159\x2db25ff8ce9b0d.device: Job dev-disk-by\x2duuid-67565b77\x2d4da7\x2d4b46\x2da159\x2db25ff8ce9b0d.device/start failed with result 'timeout'.
Aug 6 20:07:56 george-ThinkPad-T420 mate-system-mon[1548]: SELinux was found but is not enabled.
Aug 6 20:12:23 george-ThinkPad-T420 gvfsd-metadata[1341]: g_udev_device_has_property: assertion 'G_UDEV_IS_DEVICE (device)' failed
The first 1461 lines of the syslog took 72 seconds; the last eight lines took quite a bit longer,
with a number of complaints:
net.launchpad.backintime.serviceHelper
Relates to an unresolved ubuntu 18.04 bug: https://github.com/bit-team/backintime/issues/919
Aug 6 20:07:10 george-ThinkPad-T420 systemd[1]: Startup finished in 8.225s (kernel) + 3min 11.639s (userspace) = 3min 19.865s.
The numbers in the timestamps don't add up.
Why are we messing with apparmor and selinux simultaneously ?
Aug 6 20:05:40 george-ThinkPad-T420 kernel: [ 1.111361] evm: Initialising EVM extended attributes:
Aug 6 20:05:40 george-ThinkPad-T420 kernel: [ 1.111362] evm: security.selinux
...
Aug 6 20:05:40 george-ThinkPad-T420 kernel: [ 1.111364] evm: security.apparmor
...
Aug 6 20:05:40 george-ThinkPad-T420 kernel: [ 8.652182] systemd[1]: systemd 237 running in system mode. (+PAM +AUDIT +SELINUX +IMA +APPARMOR +SMACK +SYSVINIT +UTMP +LIBCRYPTSETUP +GCRYPT +GNUTLS +ACL +XZ +LZ4 +SECCOMP +BLKID +ELFUTILS +KMOD -IDN2 +IDN -PCRE2 default-hierarchy=hybrid)
...
Aug 6 20:07:56 george-ThinkPad-T420 mate-system-mon[1548]: SELinux was found but is not enabled.
See: https://linuxconfig.org/how-to-disable-enable-selinux-on-ubuntu-20-04-focal-fossa-linux/
The last step involved nearly five minutes of dithering:
Aug 6 20:12:23 george-ThinkPad-T420 gvfsd-metadata[1341]: g_udev_device_has_property: assertion 'G_UDEV_IS_DEVICE (device)' failed
Another bug: https://bugs.launchpad.net/ubuntu/+source/gvfs/+bug/1752091

The "device" problems relate to the USB 3.0-connected HDD that is located at /dev/sdc,which is apparently
a trifle slow in spinning up. When I mount it manually in order to open icedove:
mount /dev/sdc3 /media/george/Data-II
the system occasionally finds /dev/sdb2 instead and then complains that it's a swap partition.
Activating GParted first gets the three drives in their correct order; then the mount command doesn't fail.
That's the price I pay for portability of that third drive, which works on two other Lenovo T420's as well.