The server I'm hosting a few of my Matomo instances on has recently adopted a security measure for preventing bruteforce attacks.
The hosting provider staff says that part of this entails PHP variables such as $_SERVER['REMOTE_ADDR'] will return the local machine external address instead of the visitor's. As a result all the visitors in my Matomo history appear to come from the same city as the server location. Regardless what city, region or nation they visit from.
$_SERVER["HTTP_X_REAL_IP"] is the actual variable to be used on those machines, otherwise a migration to a less secure server will be necessary.
I haven't found a way to address this problem through the config file, in the docs I've only found information as for logging the real IP address when behing a proxy, which isn't my case. Is there any way to set which variable should be called for the IP address value provided by PHP?
That's probably the FAQ you found and it should in this case also apply to you even though it might not be a proxy.
Let me know if this doesn't work for you and I'll be happy to reopen.