Honestly, the best results I've gotten have been from downloading the whole book from OkadaBooks, but you have to be careful which books you pick. Some publishers label older titles as 'latest' for months. I refresh the 'New Arrivals' on the Jiji Books app a lot too, but their selection isn't huge.
What really works for me is following the writers directly on Facebook, like Bilkisu Funtuwa or Hauwa Allahbura. They announce when their new stories are complete and ready, and they'll sometimes share a direct Google Drive link to the PDF. That's how I got 'Labarin Zuciyata' a week after the final chapter was posted online. You miss out on features like bookmarking, but you get the full story fast and for free, which is the main thing for me.