[hooksfordays]

This is what I currently do with my app. The code is open source, it's free for anybody to build and install, the build steps are simply clone and build with Android Studio. I upload the debug .apk as a GitHub release with no valid keys (so no ads), but there are ads at the bottom of the screen on the play store version.

It makes a little change every month and I've not had any complaints about the ads, except to offer a pay-to-remove option, which I mostly just haven't gotten around to yet.