Yep, people here hate the organically built Lisp save and die images, but many open source and in company repositories with docker are very similar: they got it working on their computer inside docker through manually changing, rearranging and writing scripts, many of which reverse things from other scripts, update packages installed higher up in the same script etc etc and then just published it as it works. So trying 'make' or whatever outside the container simply errors out as it wont work anywhere else but in the very specific confines of the linux inside the container. The difference is pretty clear: if the readme starts with how to run the project without docker but also has a docker, the setup is clean, if it starts with docker and then, maybe, points to a separate docs dir with random 'notes' how to run locally, you know it will be a mess you probably never want to try (outside running docker).