It is worth mentioning that the M100 apparently doesn’t support local control, only local automations. If there’s no Internet or there’s an Aqara cloud outage you won’t be able to control devices with Aqara app.
According to the post and comments, there’s a LAN control option for the M3 but seems to be missing in M100.
Or maybe it can and the “problem” was that the user also had an E1 and then the whole option was disabled even if devices connected to M100 could have been controlled.
Does the M100 work offline with Aqara app if you only have a M100?