Change mix run command to task for Debugging

run is already a Mix task. Try setting your debug config to something like this:

{
  "type": "mix_task",
  "name": "Peel.scan/0",
  "request": "launch",
  "task": "run",
  "taskArgs": ["-e", "Peel.scan()"],
  "projectDir": "${workspaceRoot}"
}