When you go into Luci and select System → Logging you are able to set the levels for Log Output Level and Cron Log Level.
Log Output Level - Debug, Info, Notice, Warning, Error, Critical, Alert, Emergency
Cron Log Level - Debug, Warning, Normal
I currently get log entries every 15min when the DHCP refreshes from my ISP, as follows:
Sat Nov 13 00:40:58 2021 daemon.notice netifd: wan (11944): udhcpc: lease of IP address obtained, lease time 1800
Sat Nov 13 00:55:58 2021 daemon.notice netifd: wan (11944): udhcpc: sending renew to IP address
What would the Logging or Cron settings need to be to only show log entries when something not normal happens ??