Hi @nelson2,
I wouldn’t be that pessimistic about LinkedIn support 
To reiterate what options we have on our side:
Custom error page: The customization will allow you to adjust the value of the error_description variable for this specific error code via the Management API call to make it more informative, like:
“Hey, among other possible reasons, the error you see is probably caused by you clicking the Sign-Up button on the Liked In login widget more than once. After submitting your credentials and clicking “Sign in” there, please give it a few seconds to proceed.”
On this error page, the flow ends with no further redirection.
Setting the common Login URI for the client application. I will try to be more specific here:
The Login URI must redirect to our /authorize endpoint along with the client_id and other required parameters like organization. When Auth0 calls this Login URI, Auth0 automatically adds the organization name and organization id parameters to it, so you don’t need to know what organization the flow has initiated from. Instead, when constructing the /authorize call, make use of these added by Auth0 to the Login URI params to:
1.define the organization param of the /authorize call,
2.define the redirect_to param of the /authorize.
For the second one, the general idea is:
Get organization name from query param > build organization specific callback URL with organization name > specify that redirect_uri in login request options.