Not yet a Debian on Android, but: https://ollieparanoid.github.io/post/50-days-of-postmarketOS/
summarizes the first 50 days of building Linux directly for several smartphones, with the intention of eventually getting them fully functional. Their work could lead to a Debian flavor/spin/whatever it's called now. Personally, I would be pretty happy to run Debian on a phone instead of the giant pile of Java sitting on an old kernel that currently constitutes Android. -dsr-
