Someone just pointed out to me that you can now install AmberTools20 using conda.

conda install -c conda-forge ambertools=20

This should work for Linux and MacOS systems, but it does not provide access to parallel or gpu-optimized codes. It provides a simple way to get started with AmberTools, and to install it into many workflows, but is not a substitute for the full source-code distributions

Full details are here http://ambermd.org/GetAmber.php.