this is the main pointer

On every device (but the central syslogserver or you create a loop that fills the drive in mere seconds)

/etc/rsyslog.d/99-centralsyslog.conf

$PreserveFQDN on
*.*  @192.168.1.66

then on the central syslog server 192.168.1.66

/etc/rsyslog.d/01-syslog_receiver.conf

# provides UDP syslog reception
module(load="imudp")
input(type="imudp" port="514")

# provides TCP syslog reception
module(load="imtcp")
input(type="imtcp" port="514")

and also

/etc/rsyslog.d/20-save2postgresql.conf

# Load the PostgreSQL output module
module(load="ompgsql")

# Template for inserting logs
template(name="pgsql-template" option.sql="on" type="string" string="INSERT INTO system_events (hostname, facility, priority, tag, message) VALUES ('%HOSTNAME%', %syslogfacility%, %syslogpriority%, '%syslogtag%', '%msg%' )") 

# Send logs to PostgreSQL
*.emerg    :ompgsql:127.0.0.1,syslog,syslog_user,WeakPassword;pgsql-template
*.panic    :ompgsql:127.0.0.1,syslog,syslog_user,WeakPassword;pgsql-template
*.alert    :ompgsql:127.0.0.1,syslog,syslog_user,WeakPassword;pgsql-template
*.crit     :ompgsql:127.0.0.1,syslog,syslog_user,WeakPassword;pgsql-template
*.error    :ompgsql:127.0.0.1,syslog,syslog_user,WeakPassword;pgsql-template
*.err      :ompgsql:127.0.0.1,syslog,syslog_user,WeakPassword;pgsql-template
#*.warning  :ompgsql:127.0.0.1,syslog,syslog_user,WeakPassword;pgsql-template
#*.warn     :ompgsql:127.0.0.1,syslog,syslog_user,WeakPassword;pgsql-template
#*.notice  :ompgsql:127.0.0.1,syslog,syslog_user,WeakPassword;pgsql-template
#*.info  :ompgsql:127.0.0.1,syslog,syslog_user,WeakPassword;pgsql-template
#*.debug  :ompgsql:127.0.0.1,syslog,syslog_user,WeakPassword;pgsql-template

make sure you install postgres, the rsyslog-psql module and create the databases. Grafana can run on the same or any other server.