Tested it with the latest Kodi nightly kodi-20201222-95ec740b-master-armeabi-v7a.apk and the latest Plex for Kodi plugin https://github.com/pannal/plex-for-kodi/archive/develop_kodi19.zip today. Works flawless. Thank you very much for all the work.
I had to switch to Kodi 19 due to an audio passthrough bug with the latest Amazon OS 6.2.7.7 update on my FireTV 4k / https://forum.kodi.tv/showthread.php?tid=336151&page=89
