I have the same problem as described in Android Gradle Plugin 3.0.0-alpha4 - not picking .so libraries from local AAR
Only difference is the version of the android gradle plugin that is used, including the .so-files from the aar worked in version 3.4.2, but it is not working in version 3.5.3 and 3.6.2.
As described in the other post I also tried importing the local project with the aar with api instead of implementation, also to no avail.