Elasticsearch version (bin/elasticsearch --version): 7.14 BC4
"build_hash" : "6ef8c9df9a5605291c84fd3b5b0e1c7e16883a87",
"build_date" : "2021-07-21T23:34:08.637646613Z",

Plugins installed: [] the source cluster had the mapper_size plugin installed, the destination cluster did not. I don't believe that this is relevant since a restore would usually fail with an exception if that's the case, but maybe there's an edge case for data streams.

JVM version (java -version): Elastic Cloud

OS version (uname -a if on a Unix-like system): Elastic Cloud

Description of the problem including expected versus actual behavior:

After restoring a snapshot, the cluster gets locked down and most APIs are not accessible anymore

As an example a GET _cat/indices

  "error" : {
    "root_cause" : [
      {
        "type" : "security_exception",
        "reason" : "action [indices:monitor/settings/get] is unauthorized for user [3612216885] with roles [superuser], this action is granted by the index privileges [monitor,view_index_metadata,manage,all]"
      }
    ],
    "type" : "security_exception",
    "reason" : "action [indices:monitor/settings/get] is unauthorized for user [3612216885] with roles [superuser], this action is granted by the index privileges [monitor,view_index_metadata,manage,all]",
    "caused_by" : {
      "type" : "illegal_state_exception",
      "reason" : "system index is part of a data stream that is not a system data stream"
    }
  },
  "status" : 403
}

Steps to reproduce:
I will share the steps to reproduce internally in slack as this snapshot bucket can not be shared publicly

Provide logs (if relevant):