<an eternity later…> Yo yo OP! Here is my sample Preferences.xml, I have nulled out the fields you will need to fill up from the windows registry. After this I still had to reshare the libraries with my friends, unsure which step I botched, but that was easy to re-do.

<?xml version="1.0" encoding="utf-8"?>
<Preferences
OldestPreviousVersion="1.18.3.2156-349e9837e"
MachineIdentifier="####################"
ProcessedMachineIdentifier="####################"
AnonymousMachineIdentifier="####################"
MetricsEpoch="1"
AcceptedEULA="1"
PublishServerOnPlexOnlineKey="1"
PlexOnlineToken="####################"
PlexOnlineUsername="####################"
PlexOnlineMail="####################"
LastAutomaticMappedPort="0"
CertificateVersion="3"
PubSubServer="####################"
PubSubServerRegion="fmt"
PubSubServerPing="485"
LanguageInCloud="1"
FriendlyName="####################"
TranscodeCountLimit="3"
TranscoderQuality="0"
TranscoderH264BackgroundPreset="medium"
ButlerUpdateChannel="0"
DlnaEnabled="0"
CinemaTrailersFromTheater="1"
CinemaTrailersType="0"
WanPerUserStreamCount="2"
LanNetworksBandwidth=""
allowedNetworks="192.168.1.0/24"
customConnections=""
ManualPortMappingMode="1"
ManualPortMappingPort="####################"
FSEventLibraryPartialScanEnabled="0"
FSEventLibraryUpdatesEnabled="0"
GenerateBIFBehavior="never"
OnDeckWindow="52"
ScannerLowPriority="0"
ScheduledLibraryUpdateInterval="86400"
ScheduledLibraryUpdatesEnabled="1"
watchMusicSections="1"
CloudSyncNeedsUpdate="0"
ButlerTaskRefreshLibraries="1"
MinutesAllowedPaused="30"
DlnaReportTimeline="0"
ButlerEndHour="7"
ButlerStartHour="3"
PlexOnlineHome="0"
DvrIncrementalEpgLoader="0"
EnableIPv6="0"
WebHooksEnabled="0"
CinemaTrailersPrerollID=""
TranscoderCanOnlyRemuxVideo="0"
PushNotificationsEnabled="0"
LogVerbose="0"
MergedRecentlyAdded="0"
ButlerTaskCleanOldBundles="1"
ButlerTaskCleanOldCacheFiles="1"
ButlerTaskDeepMediaAnalysis="1"
ButlerTaskGenerateAutoTags="0"
ButlerTaskOptimizeDatabase="1"
ButlerTaskRefreshLocalMedia="1"
ButlerTaskRefreshPeriodicMetadata="1"
ButlerTaskReverseGeocode="0"
ButlerTaskUpgradeMediaAnalysis="1"
GenerateChapterThumbBehavior="never"
GenerateIntroMarkerBehavior="never"
LoudnessAnalysisBehavior="never"
MusicAnalysisBehavior="never"
WanTotalMaxUploadRate="20000"
autoEmptyTrash="1"
GlobalMusicVideoPathMigrated="1"
CertificateUUID="####################"
secureConnections="1"
DatabaseCacheSize="4000"
ButlerTaskBackupDatabase="1"
customCertificatePath=""
PreferredNetworkInterface="eno1"
CinemaTrailersFromBluRay="1"
ButlerDatabaseBackupPath="/var/lib/plexmediaserver/Library/Application Support/Plex Media Server/Plug-in Support/Databases"
sendCrashReports="1"
HardwareDevicePath="####################"/>

On the phone right now, but i did this last month OP.

First of all make sure to keep a backup of the db. Normally Plex does this for you every few days in the db folder. (From your old windows install)

The missing ingredient most likely is converting all the windows registry entries into preferences.xml

There was a reddit post where some one had posted a sample XML. I repopulated it with all the settings from the windows registry export. If you can’t find the post then I can post mine here in the morning.

Also had to create a plex user and group and chown it to all the media. I am a new Linux user so had to fuck around a lot coz of Fedoras SELinux file perms.