Basically - no more kern.log, syslog in in /var/log. Instead you access the equivalent via the journal.
Looking rsyslog also provides files for auth.log, mail., news. and ufw from the default install. For completeness here are the equivalent commands:
kern.log - journalctl -k
syslog - journalctl -b 0 (where 0 is current boot, if you want 2 boots ago, use -2 or you can just use no argument for all)
auth.log - you can either just do the whole journal or select the auth service you are interested. for example, journalctl -b 0 -u systemd-logind
mail., news. - not relevant for desktop?
UFW can just search for the keyword
In my testing, apt/*, dpkg.log, apport.log, and gpu-manager.log all seem to write directly to /var/log so shouldn’t be impacted by this change.