All versions of Androidplot up to 1.5.7 are available through Maven Central.
Going forward, hosting artifacts on Github Packages is a possibility as that is a straight forward implementation. Would love to continue publishing artifacts to Maven Central but that's going to require a bit of time to work through getting the CI to publish to Sonatype.
Either way, worst case is you'll need to add the Github Packages repository to your build script (3 lines to copy/paste)