You can use the generic Resource List endpoint and filter it by things like name and resource type without specifying resource group, but this will still require a subscription ID: https://learn.microsoft.com/en-us/rest/api/resources/resources/list
If you needed to do this without a subscription ID, you would need to loop through the subscriptions available to that user and test each one to find the specific VM. I do understand that this might not be ideal in a case where a login has access to many subscriptions.