Plex in docker with binds
The problem is that Plex runs as the plex user and therefore is not possible to access the bindings.
Find /etc/services.d/plex/run and change the line
exec s6-setuidgid plex /bin/sh -c 'LD_LIBRARY_PATH=/usr/lib/plexmediaserver /usr/lib/plexmediaserver/Plex\ Media\ Server'
to
exec s6-setuidgid root /bin/sh -c 'LD_LIBRARY_PATH=/usr/lib/plexmediaserver /usr/lib/plexmediaserver/Plex\ Media\ Server'