Hi Daniel,
The local ip should be the docker's IP,not the Host IP
Make sure to add the configuration inside <ossec_config> block of ossec.conf of the manager
I have added a sample configuration for your reference.
<remote>
<connection>syslog</connection>
<port>514</port>
<protocol>tcp</protocol>
<allowed-ips>192.168.100.1/32</allowed-ips>
<local_ip>192.168.65.145</local_ip>
</remote>
Please do not update the <remote> configuration block that is already there by default for agent connection.
Ref: https://documentation.wazuh.com/current/user-manual/capabilities/log-data-collection/syslog.html
Let me know if this solves your issue.