You mention the Chinese library. There was a time, 6 or 7 years ago, when the Chinese library was actually the worst of all the LingQ libraries - in terms of available content. It only took a handful, or so, of people to build it up.
Some ways to possibly find content:
-hang out on Greek language learning posts and subs at reddit and see what materials get mentioned, ask questions about resources
-trawl through major Greek news sites, esp for text and audio
-learn what the most common search terms in Greek are for audio and text, mp3 and transcript, podcast and transcript etc – then google these terms extensively
-search the major Greek youtube channels, particularly for the names of major tv stations or tv programs, with the search filter additionally set for “subtitles/CC”
-go to italki and hang out in the “answers” and “discussions” sections, with filter set for Greek, ask questions about resources
-go to itunes, then podcasts, then set your language to Greek and look at the most popular native podcasts - search for transcripts of these podcasts - if can’t get transcripts - post on upwork for someone to make up transcripts cheaply
-start a thread on language learning sites – listing Greek resources you have found and invite others to add
-find any dedicated Greek language learning forums and hang out there looking for resources
-get together with other LingQ members learning Greek and pool together to create content - eg along the lines of this thread – https://www.lingq.com/forum/1/31709/
If you get permission to share content, I’d encourage you to do so. Not least, because sharing content forces you to really go through a lesson and check to see if it is worth publishing and try to remove as many errors as possible - this act, in and of itself, is really useful for building up your ability in that language.