I havent actually seen anything on whether the Graviton processor supports 32-bit mode (its an optional extension for ARMv8); does anyone know if it does?
I was able to build ros-kinetic-catkin using the ros_buildfarm `generate_release_script.py` on an a1.medium instance. Build performance wasn't bad. Python 3 performance on the host seemed (mostly generating the build script) seemed dramatically worse than amd64. Taking 20-25 seconds instead of 3-5 seconds. So it looks like armv7 instructions are supported by these instances.