This issue is a major problem for me and it looks like it has been festering for years. My setup is a little different from the OPās, but the issue is the same.
I run the Plex Media server on a Synology NAS ( Version 1.16.5.1554). I have it set to use embedded metadata when present and metadata is present on all my library files. In particular, compilations have Album Artist set to either āVarious Artistsā or some other meaningful value.
When I play the tracks on a Plex client (I have tested web, android and an Android TV) then album information is shown correctly with the Album Artist that is set in the ID3v2.3 (or in rare cases ID3v2.4) tag. Playing individual tracks, however, the artist that is set in the Artis field of the metadata is displayed. This to my mind is the correct behaviour.
When I cast the track from the Plex client (web or Android) to a chromecast, the artist is displayed on screen I am casting to as Various Artists or whatever else is set in the Album Artist field. The Plex client continues to display the artist correctly.
Similarly, if I enable the DLNA server on the PMS, and then request tracks from the Plex DLNA server, once again the Artist is incorrectly displayed as āVarious Artistsā.
If I use the Synology Media Server as the DLNA server, serving from the same media files, the artist is displayed correctly so the problem seems to be with PMS rather than a general issue with the DLNA protocols.
I tried stripping the Album Artist field altogether from the tracks, leaving it blank for compilations to see if this would force Plex to use the information in the Artist field. However Plex is too smart for me. When the Album Artist field is blank, it enters it in the library as having Album Artist āVarious Artistsā (without actually writing to the tag) and the problem persists. If I play those tracks then they display as having artist āvarious artistsā.
Additionally, if I go to listings by artist, PMS seems only to read the Album Artist tags and not the Artist tags so tracks in compilations do not show up.