I think waiting for the apt locks to be released with something like this would work
startup_bash_script = [ "#!/bin/bash", "while sudo fuser /var/{lib/{dpkg,apt/lists},cache/apt/archives}/lock >/dev/null 2>&1; do echo 'Waiting for other instances of apt to complete...'; sleep 5; done", "sudo apt-get update", ...Weirdly this throws an error in the autoscaler:
Spinning new instance type=v100_spot Error: Failed to start new instance, unexpected '{' in field name