Tell apart systemd journal logs from machines

Hi,
I’ve been trying out Alloy for a little by now and I’ve set up a local Loki instance which receives Systemd Journal logs from multiple machines with Alloy, here’s the Alloy config of the machines:

loki.relabel "journal" {
  forward_to = []
  rule {
    source_labels = ["__journal__systemd_unit"]
    target_label  = "unit"
  }
}

loki.source.journal "journalctl"  {
  forward_to    = [loki.write.main_loki.receiver]
  relabel_rules = loki.relabel.journal.rules
  labels        = {
    component = "loki.source.journal",
    instance = constants.hostname,
  }
}

loki.write "main_loki" {
   endpoint {
      url = "http://loki:3100/loki/api/v1/push"
   }
}

It works fine but here’s my question, how do I tell apart from which machine the logs are from? Right now I’m adding an instance label to the logs with the hostname of the machine sending the logs, but that leaves the responsibility of identification to the Alloy client.
I wanted to ask if there’s some way to identify the origin machines from the Loki instance or an Alloy proxy.
I know i could make an Alloy proxy with a different listener for each machine but i don’t think that scales too well.

Thank you in advance.