I have an LG WebOS TV that can only support *.srt subtitles and a Linux home server.
I did a lot of search, but I can not find any media service software that supports *.sup subtitles (HDMV PGS) inside mkv files.
I tried plex, jellyfin, emby, kodi and minidlna. Some of them can transcode video and sound that my TV not supported, but none of them can transcode the sup subtitle.
