XML included below, as well as the output from metaflac --list. Is plex able to read FLAC tags?
Structure of albums is /media/Music/random_folder_name/artist/album/various_track_naming_conventions.mp3-flac-whatever
user@machine:/media/Music/folder/AC-DC/Back in Black [24-96 Vinyl]$ metaflac --list A1\ -\ Hells\ Bells.flac
METADATA block #0
type: 0 (STREAMINFO)
is last: false
length: 34
minimum blocksize: 4096 samples
maximum blocksize: 4096 samples
minimum framesize: 2597 bytes
maximum framesize: 18620 bytes
sample_rate: 96000 Hz
channels: 2
bits-per-sample: 24
total samples: 29850110
MD5 signature: b554bdb599376440fd9db9d0f78acc36
METADATA block #1
type: 3 (SEEKTABLE)
is last: false
length: 576
seek points: 32
point 0: sample_number=0, stream_offset=0, frame_samples=4096
point 1: sample_number=958464, stream_offset=2957180, frame_samples=4096
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point 31: sample_number=29757440, stream_offset=112842335, frame_samples=4096
METADATA block #2
type: 4 (VORBIS_COMMENT)
is last: false
length: 2030
vendor string: reference libFLAC 1.2.1 20070917
comments: 15
comment[0]: TITLE=Hells Bells
comment[1]: ARTIST=AC/DC
comment[2]: ALBUM ARTIST=AC/DC
comment[3]: ALBUMARTIST=AC/DC
comment[4]: ALBUM=Back In Black [Vinyl]
comment[5]: TRACKNUMBER=01
comment[6]: COMMENT=2003 - Sony Music / E 80207 / 180g EU Pressing / Vinyl
Technical Log:
blah blah blah
comment[7]: GENRE=Hard Rock
comment[8]: DATE=2003
comment[9]: ENSEMBLE=AC/DC
comment[10]: REPLAYGAIN_TRACK_PEAK=0.798706
comment[11]: REPLAYGAIN_TRACK_GAIN=-0.840000 dB
comment[12]: REPLAYGAIN_ALBUM_GAIN=-1.080000 dB
comment[13]: TOTALTRACKS=10
comment[14]: LABEL=Sony Music
<MediaContainer size="1" allowSync="1" identifier="com.plexapp.plugins.library" librarySectionID="4" librarySectionTitle="Music" librarySectionUUID="51f171b2-4220-48fd-9bc3-5ea8bd51e05e" mediaTagPrefix="/system/bundle/media/flags/" mediaTagVersion="1537530240">
<Track ratingKey="5911" key="/library/metadata/5911" parentRatingKey="5910" grandparentRatingKey="5838" guid="com.plexapp.agents.lastfm://AC/DC/Back%20In%20Black%20%5BVinyl%5D/1?lang=en" librarySectionTitle="Music" librarySectionID="4" librarySectionKey="/library/sections/4" type="track" title="Hells Bells" grandparentKey="/library/metadata/5838" parentKey="/library/metadata/5910" grandparentTitle="AC/DC" parentTitle="DC" originalTitle="AC/DC" summary="" index="1" parentIndex="1" ratingCount="1207" viewCount="3" lastViewedAt="1536438161" thumb="/library/metadata/5910/thumb/1541426619" art="/library/metadata/5838/art/1541300292" parentThumb="/library/metadata/5910/thumb/1541426619" grandparentThumb="/library/metadata/5838/thumb/1541300292" grandparentArt="/library/metadata/5838/art/1541300292" duration="310939" addedAt="1452677575" updatedAt="1541426617">
<Media id="5176" duration="310939" bitrate="2912" width="500" height="456" aspectRatio="1.33" audioChannels="2" audioCodec="flac" videoCodec="mjpeg" container="flac">
<Part accessible="1" exists="1" id="5176" key="/library/parts/5176/1415621840/file.flac" duration="310939" file="/media/Music/folder/AC-DC/Back in Black [24-96 Vinyl]/A1 - Hells Bells.flac" size="113164136" container="flac" hasThumbnail="1">
<Stream id="5198" streamType="2" selected="1" codec="flac" index="0" channels="2" bitrate="2911" albumGain="-3.05" albumPeak="0.959848" albumRange="5.738934" audioChannelLayout="stereo" bitDepth="24" bitrateMode="vbr" duration="310938" gain="-2.76" loudness="-15.24" lra="8.31" peak="0.798729" samplingRate="96000" displayTitle="Unknown (FLAC Stereo)"/>
<Stream id="1026120" key="/library/streams/1026120" streamType="4" codec="lrc" format="lrc" minLines="3" provider="com.plexapp.agents.lyricfind" timed="1" displayTitle="Unknown (LRC External)"/>
<Stream id="1026121" key="/library/streams/1026121" streamType="4" codec="txt" format="txt" provider="com.plexapp.agents.lyricfind" displayTitle="Unknown (TXT External)"/>
</Part>
</Media>
<Extras size="0"> </Extras>
</Track>
</MediaContainer>