If rsyslog is no longer needed (mark package install as auto to find out).

Make sure systemd journal is persistent if that is what you want.

Check folder /var/log/journal/*/ to verify.

Then the following old log files can be removed too.

rm /var/log/auth.log*
rm /var/log/cron.log*
rm /var/log/daemon.log*
rm /var/log/debug*
rm /var/log/kern.log*
rm /var/log/lpr.log*
rm /var/log/mail.err*
rm /var/log/mail.info*
rm /var/log/mail.log*
rm /var/log/mail.warn*
rm /var/log/messages*
rm /var/log/syslog*
rm /var/log/user.log*