Does android keeps a system log about location and networks? I'm working together with the local authorities to try to identify where a phone was during the last few days. Some pictures were taken but GPS was turned off. Is there any clue that we could get from the local logs about the location of such images, like available networks? If so, where should we look at?
Device using: Android 8.0
By default Android does not save any local logs, even the logcat log is just a ring buffer that contains only the last log elements that fit into the log buffer (often this buffer has ~65KB).
Typically such abuffer is overwritten after a few hours, if the device use not used it may last up to one or two days but that is very device specific. Some devices log dozens of messages per minute even in Air-plane mode without any app active.
First you should check if the location services are activated at all. If they are not activated there is a high chance that they aware deactivated all the time and hence no app was able to access any location.
As far as I know Android itself does not record data on available or used mobile network  bases or Wifi access points. Only if Google location services are activated such data is collected and uploaded to Google.
If you have support of the local authorities the easiest way would be to contact the mobile network provider the used SIM-card is from and use their log which antennas were used in the specified time span.