Creating a redirect for users without a login name, but user.login has a mystery default value

iftomkins - As I was looking through it, I couldn't find any flag being set for the users who have not created the login name on the community. However, while checking the V2 API, I found that the SSO users who have not created a username yet does not get any data in the V2 response. I am not sure if this would work for your case because the username is already being set from the profile defaults as 'SunsetRunner', but it is worth checking anyways. Here is the V2 resource I am referring to.

One of our communities also has the SSO, but I did not find the option for setting a default name for deleted user.

I tried the following V2 calls:

SELECT registration_data.status FROM users WHERE id = '47' - This is the registered user with login name created in the community.

SELECT registration_data.status FROM users WHERE id = '386' - This is the user who has SSO a/c but haven't yet created a username in community.

the first call returns the status as "status" : "fully-registered"

{
  "status" : "success",
  "message" : "",
  "http_code" : 200,
  "data" : {
    "type" : "users",
    "list_item_type" : "user",
    "size" : 1,
    "items" : [ {
      "type" : "user",
      "registration_data" : {
        "type" : "registration_data",
        "status" : "fully-registered"
      }
    } ]
  },
  "metadata" : { }
}

The second one:

{
  "status" : "success",
  "message" : "",
  "http_code" : 200,
  "data" : {
    "type" : "users",
    "list_item_type" : "user",
    "size" : 0,
    "items" : [ ]
  },
  "metadata" : { }
}

If it is same in your case, I believe you have got the solution for this. I hope this helps.