Quill's route has been released.
There is nothing in particular you need to do to get to his route. It unlocks naturally with a specific choice in the common route (choose to hide instead of run when giving the option during the sequence where the MC is in the abandoned district.)
While it shouldn't be required, please consider starting a new game to begin his route.
There shouldn't be any save compatibility issues, however, there were minor changes to some of the other routes (primarily typo fixes or minor wording changes for continuity) as well. If you do run into a game-breaking error after loading an old save, please start a new game and see if the error still occurs before you report it.
Reuben's route is the next route I am working to complete. It is currently about 60% drafted and my focus for the next month or two will be getting it drafted and fully edited.
~Esh