Okay, I’ve come up with this little snippet. Is there anything that could be improved with it?

  def start_node(number) when number > 20, do: raise "Too many instances found"
  def start_node(number \\ 0) do
    node_name = node_name(number)

    case Node.start(node_name, :shortnames) do
      {:error, _error} ->
        start_node(number + 1)

      {:ok, _pid} ->
        IO.puts("Started node with name #{inspect(node_name)}")
        Node.set_cookie(node_name, :cookie)

        for num <- Range.new(0, number) do
          Node.connect(node_name)
        end
    end
  end

  def node_name(number) do
    {:ok, hostname} = :inet.gethostname()

    "elixirls-#{number}@#{hostname}"
    |> String.to_atom()
  end

Edit: added a max number

This is only for a local machine, so I think short names should be fine, in fact if I could I would ignore the hostname completely in this code. Also Node.start/3 and Node.connect/1 both only accept atoms so the only way that I see to avoid String.to_atom/1 is to pregenerate a set number of node names. Which could be a good idea, but if I were to do that I’d prefer to instead just limit the number that start_node will recurse to, a max of 20 would probably be a good idea.