I tried installing ROS manually using the steps described in the Dockerfile for melodic-ros-core-alpine, the following step is failing: rosdep install -y --from-paths src --ignore-src
When trying to install sbcl on armhf there are several packages failing, the most critical one is clisp which cannot be built on armhf processor (RPi3B+ with arm7l Alpine 3.8).
Apparently there are no prebuilt packages for clisp nor sbcl for Alpine.