VM is a virtual machine or loosely speaking something providing containerisation. It provides a solution for running applications built for other OS’s by allowing for different operating systems to run inside the host OS installed on the computer - in your case Chrome OS 80 as host and as your info above Debian Buster in the container.
So for my part in any troubleshooting things I am thinking about at the moment:
- Why SNAPS aren’t installing on Debian Buster
- Is there potentially a problem with the container network bridging between Chrome OS and Debian Buster that needs to be sorted.
Maybe try sudo snap install atom