I do some reading with Moon+ reader on my phone when I'm away from my Kindle and it has a page number option that shows total screens in chapter and number of screens already read. That gives you a pretty good idea of where you are in the chapter.
Of course if you change fonts or line spacing or margins these numbers change. That makes it difficult if you're always changing the layout but for people like me who rarely do this I think it's the most rational plan I've seen.
Moon+ should never have been named Moon+. It should have been called Rational Reader or some such.
Barry