it’s pointless to save logs without IP addresses but it’s your wish…
I think you can’t do this by default… so it requires some post-processing. thankfully nextcloud.log and audit.log are stored in JSON format and you can easily parse them using jq command… you can easily choose to only display required logs fields and omit IP addresses at all (but in audit logs you will see an acting user as well so the IP address is likely less PII than username)
see an example