As the title says, Matomo shows a visitor with an IP address which is not in the apache logs. How can this be?
Is your server behind a proxy?
No, it is not behind a proxy.
When you write:
Are the IPs displayed by Matomo all finishing by
.0 whereas Apache ones are not?
Has the visit been added by an API command?
For example using the HTTP tracker API one could create a visit to track in Matomo without visiting the website. For example, https://your-matomo-instance/matomo.php?idsite=1&rec=1&apiv=1&_id=0000000000000021&url=https://domain.com/pagename