Drush stuck in "Killed" loop
I haven't found a solution to the "Killed" loop issue (even after scaling up to the largest instance offered by my host, which has 64GB of RAM), but I've managed to get drush itself to work by pulling the .phar from Github and making it executable.

Using the install script still doesn't work (still leads to the Killed loop) despite making sure that everything that should be executable is executable, and installing from the tarballs or via composer likewise fails in a similar way.