Ubuntu – Random freezes on 19.04, unsure which logs to check

I have scoured both Askubuntu as well other sites for this and haven't found anything substantial, so I hope it's not too much of a duplicate.

In any case, I've been lately experiencing random freezes – the system locks up completely, my keyboard and mouse do not respond, the PC also disappears from active network clients (by scanning my network with nmap from a different PC) so I assume it dies completely instead of just losing the inputs. It started happening recently, after upgrading to 19.04.

I haven't been able to pinpoint the problem, and the only common denominator seems to be Chrome. However, even then there's a huge window of variation, as I can be doing anything from watching YT to just reading Latex formatting tips, so anything from high to low load. I have GPU acceleration and other experimental goodies turned off, so I don't think it's that – besides, I never had such problems before 19.04.

The following comes up in /var/log/syslog just before the freeze:

Sep 25 12:31:08 meeshbox systemd[1]: Started Run anacron jobs.
Sep 25 12:31:08 meeshbox anacron[11822]: Anacron 2.3 started on 2019-09-25
Sep 25 12:31:08 meeshbox anacron[11822]: Normal exit (0 jobs run)
Sep 25 12:31:08 meeshbox systemd[1]: anacron.service: Succeeded.
Sep 25 12:31:32 meeshbox org.gnome.Shell.desktop[1329]: Window manager warning: Window 0x3802c74 sets an MWM hint indicating it isn't resizable, but sets min size 1 x 1 and max size 2147483647 x 214748364
7; this doesn't make much sense.
Sep 25 12:31:32 meeshbox org.gnome.Shell.desktop[1329]: Window manager warning: Window 0x3802c74 sets an MWM hint indicating it isn't resizable, but sets min size 1 x 1 and max size 2147483647 x 214748364
7; this doesn't make much sense.
Sep 25 12:36:28 meeshbox org.gnome.Shell.desktop[1329]: [1:1:0925/123628.789445:ERROR:child_process_sandbox_support_impl_linux.cc(81)] FontService unique font name matching request did not receive a respo
nse.
Sep 25 12:36:28 meeshbox org.gnome.Shell.desktop[1329]: [1:1:0925/123628.791155:ERROR:child_process_sandbox_support_impl_linux.cc(81)] FontService unique font name matching request did not receive a respo
nse.
Sep 25 12:36:45 meeshbox org.gnome.Shell.desktop[1329]: Window manager warning: Window 0x38039d7 sets an MWM hint indicating it isn't resizable, but sets min size 1 x 1 and max size 2147483647 x 214748364
7; this doesn't make much sense.
Sep 25 12:36:45 meeshbox org.gnome.Shell.desktop[1329]: Window manager warning: Window 0x38039d7 sets an MWM hint indicating it isn't resizable, but sets min size 1 x 1 and max size 2147483647 x 214748364
7; this doesn't make much sense.
Sep 25 12:38:08 meeshbox org.gnome.Shell.desktop[1329]: Window manager warning: Window 0x3803b5a sets an MWM hint indicating it isn't resizable, but sets min size 1 x 1 and max size 2147483647 x 214748364
7; this doesn't make much sense.
Sep 25 12:38:08 meeshbox org.gnome.Shell.desktop[1329]: Window manager warning: Window 0x3803b5a sets an MWM hint indicating it isn't resizable, but sets min size 1 x 1 and max size 2147483647 x 2147483647; this doesn't make much sense.
Sep 25 12:38:26 meeshbox org.gnome.Shell.desktop[1329]: Window manager warning: Window 0x3803bc3 sets an MWM hint indicating it isn't resizable, but sets min size 1 x 1 and max size 2147483647 x 2147483647; this doesn't make much sense.
Sep 25 12:38:26 meeshbox org.gnome.Shell.desktop[1329]: Window manager warning: Window 0x3803bc3 sets an MWM hint indicating it isn't resizable, but sets min size 1 x 1 and max size 2147483647 x 2147483647; this doesn't make much sense.
Sep 25 12:38:40 meeshbox org.gnome.Shell.desktop[1329]: Window manager warning: Window 0x3803c21 sets an MWM hint indicating it isn't resizable, but sets min size 1 x 1 and max size 2147483647 x 2147483647; this doesn't make much sense.
Sep 25 12:38:40 meeshbox org.gnome.Shell.desktop[1329]: Window manager warning: Window 0x3803c21 sets an MWM hint indicating it isn't resizable, but sets min size 1 x 1 and max size 2147483647 x 2147483647; this doesn't make much sense.
Sep 25 12:38:41 meeshbox org.gnome.Shell.desktop[1329]: Window manager warning: Window 0x3803c35 sets an MWM hint indicating it isn't resizable, but sets min size 1 x 1 and max size 2147483647 x 2147483647; this doesn't make much sense.
Sep 25 12:38:41 meeshbox org.gnome.Shell.desktop[1329]: Window manager warning: Window 0x3803c35 sets an MWM hint indicating it isn't resizable, but sets min size 1 x 1 and max size 2147483647 x 2147483647; this doesn't make much sense.
Sep 25 12:38:42 meeshbox org.gnome.Shell.desktop[1329]: Window manager warning: Window 0x3803c49 sets an MWM hint indicating it isn't resizable, but sets min size 1 x 1 and max size 2147483647 x 2147483647; this doesn't make much sense.
Sep 25 12:38:42 meeshbox org.gnome.Shell.desktop[1329]: Window manager warning: Window 0x3803c49 sets an MWM hint indicating it isn't resizable, but sets min size 1 x 1 and max size 2147483647 x 2147483647; this doesn't make much sense.
Sep 25 12:38:51 meeshbox org.gnome.Shell.desktop[1329]: Window manager warning: Window 0x3803ca1 sets an MWM hint indicating it isn't resizable, but sets min size 1 x 1 and max size 2147483647 x 2147483647; this doesn't make much sense.
Sep 25 12:38:51 meeshbox org.gnome.Shell.desktop[1329]: Window manager warning: Window 0x3803ca1 sets an MWM hint indicating it isn't resizable, but sets min size 1 x 1 and max size 2147483647 x 2147483647; this doesn't make much sense.
Sep 25 12:39:02 meeshbox org.gnome.Shell.desktop[1329]: Window manager warning: Window 0x3803d01 sets an MWM hint indicating it isn't resizable, but sets min size 1 x 1 and max size 2147483647 x 2147483647; this doesn't make much sense.
Sep 25 12:39:02 meeshbox org.gnome.Shell.desktop[1329]: Window manager warning: Window 0x3803d01 sets an MWM hint indicating it isn't resizable, but sets min size 1 x 1 and max size 2147483647 x 2147483647; this doesn't make much sense.
Sep 25 12:40:09 meeshbox smartd[910]: Device: /dev/sdb [SAT], SMART Usage Attribute: 190 Airflow_Temperature_Cel changed from 68 to 67
Sep 25 12:40:09 meeshbox smartd[910]: Device: /dev/sdb [SAT], SMART Usage Attribute: 194 Temperature_Celsius changed from 32 to 33
Sep 25 12:41:14 meeshbox systemd-resolved[803]: Server returned error NXDOMAIN, mitigating potential DNS violation DVE-2018-0001, retrying transaction with reduced feature level UDP.

Nothing of interest in kern.log. Never had this problem with 18.04. It's not very common, but quite irritating once it happens – for example now, I lost a pretty substantial chunk of code I was writing, as I was dumb enough not to save it. It also never happened when, for example, playing games, even with other stuff in the background. I cannot really pinpoint it properly. However, scouring logs from the last week for when the freezes happened, I found that lines like this:

[1:1:0925/123628.789445:ERROR:child_process_sandbox_support_impl_linux.cc(81)] FontService unique font name matching request did not receive a response.

are often seen shortly before a freeze – but not immediately before it, more like 3-4 minutes.

What other logs can be relevant to check?