Yeah, this Github packages thing is new to me. I guess it is plausible.
I tend to google “package maven” to find whatever dependency I need from Maven Central. JCenter as secondary, but it is apparently taken out at some point (Sunset on May 1st: Bintray, JCenter).
Jitpack is my third source. It is very handy if one wants to fork a project on Github and use it as a dependency. How to explain it… Well one can upload anything there and reference it through Gradle.