As @marguedas well put it, AppArmor support has not necessarily been dropped from SROS2, but rather not yet implemented. My present focus has been integrating ROS2 with DDS Security, and have not yet had time to expand upon the apparmor profile to support ROS2. Another reason is that I haven’t yet surveyed ROS2’s installation structure yet, as the majority of the apparmor profile library for ROS1 helps users to author profiles of there own by abstracting the ROS1 file directory layout.
However, as mentioned before, apparmor support is somewhat orthogonal to SROS2 interrogation with DDS Security, and so could be developed in parallel. I would certainly invite contributions and pull requests from the rest of the community to add support for ROS2, or help review what currently exists for ROS1.