Hope you get some kind of response from the Plex team, some folks have had success in improving download speeds by toggling the “Use Background Download” in Settings/Download.
My issue isn’t quite as bad as your one, however when download speeds are 1/6th in Plex as what Infuse and other solutions provide, something is wrong - Plex Downloads - VERY SLOW even on local lan!? - #13 by ozsmac
