Plex Media Server - allow other networks to connect

Edit Preferences.xml (on ubuntu it’s in /var/lib/plexmediaserver/Library/Application Support/Plex Media Server)

Add the options that you want to change, see the link below for documentation on options:

 
<?xml version="1.0" encoding="utf-8"?>
<Preferences MachineIdentifier="a770b538-7ad3-4d13-92de-20f2e234973b" 
ProcessedMachineIdentifier="bce05e0ac10270bc1fce0bf031059058d73f36f2" 
AcceptedEULA="1" FSEventLibraryUpdatesEnabled="1" collectUsageData="0" 
logDebug="0" ScheduledLibraryUpdateInterval="43200" 
ScheduledLibraryUpdatesEnabled="1" 
FriendlyName="boccob.olympus" autoScanMusicSections="1" 
allowedNetworks="192.168.0.0/255.255.0.0"/>

Source:

https://support.plex.tv/hc/en-us/articles/201105343-Advanced-Server-Settings