I don't think any recent development is happening.
(And I think you are correct, there seems to be a new flavor of PDF that even my PC, with the latest 'Reader' updates, balks at)
I have been using the last Jinke release (No TTS) to read EPUB.
I like this one over the others because: Like the original release, Last read was 4 Pages long (32 books).
I was having problems seeing the Bookshelf entries because of all the 'eye candy' decorations on the Lbook versions (I did like the Long Press Menu options)