The Wikidata notability policy disallows sitelinks to Page and Index namespaces, however, they are not disabled at software level, which makes Special:UnconnectedPages polluted. Please disable Wikidata stielinks pointing to the following namespaces:
InitialiseSettings.php
'wgProofreadPageNamespaceIds' => [ 'default' => [ 'page' => 250, 'index' => 252 ], 'test2wiki' => [ 'page' => 104, 'index' => 106 ], 'sourceswiki' => [ 'page' => 104, 'index' => 106, ], 'enwikisource' => [ 'page' => 104, 'index' => 106, ], 'arwikisource' => [ 'page' => 104, 'index' => 106, ], 'aswikisource' => [ // T45129 'page' => 104, 'index' => 106, ], 'bewikisource' => [ 'page' => 104, 'index' => 106, ], 'bnwikisource' => [ 'page' => 104, 'index' => 102, ], 'brwikisource' => [ 'page' => 102, 'index' => 100, ], 'cawikisource' => [ 'page' => 102, 'index' => 104, ], 'cywikisource' => [ 'page' => 104, 'index' => 106, ], 'dawikisource' => [ 'page' => 104, 'index' => 106, ], 'dewikisource' => [ 'page' => 102, 'index' => 104, ], 'elwikisource' => [ 'page' => 100, 'index' => 102, ], 'eowikisource' => [ 'page' => 104, 'index' => 106, ], 'eswikisource' => [ 'page' => 102, 'index' => 104, ], 'etwikisource' => [ 'page' => 102, 'index' => 104, ], 'fawikisource' => [ 'page' => 104, 'index' => 106, ], 'frwikisource' => [ 'page' => 104, 'index' => 112, ], 'frrwiki' => [ 'page' => 102, 'index' => 104 ], 'guwikisource' => [ 'page' => 104, 'index' => 106 ], 'hewikisource' => [ 'page' => 104, 'index' => 112, ], 'hrwikisource' => [ 'page' => 102, 'index' => 104, ], 'huwikisource' => [ 'page' => 104, 'index' => 106, ], 'hywikisource' => [ 'page' => 104, 'index' => 106, ], 'idwikisource' => [ 'page' => 104, 'index' => 102, ], 'itwikisource' => [ 'page' => 108, 'index' => 110, ], 'knwikisource' => [ 'page' => 104, 'index' => 106, ], 'lawikisource' => [ 'page' => 104, 'index' => 106, ], 'mlwikisource' => [ 'page' => 106, 'index' => 104, ], 'mrwikisource' => [ 'page' => 104, 'index' => 106, ], 'nlwikisource' => [ 'page' => 104, 'index' => 106 ], 'nowikisource' => [ 'page' => 104, 'index' => 106 ], 'plwikisource' => [ 'page' => 100, 'index' => 102, ], 'pmswikisource' => [ 'page' => 102, 'index' => 104, ], 'ptwikisource' => [ 'page' => 106, 'index' => 104, ], 'rowikisource' => [ 'page' => 104, 'index' => 106, ], 'ruwikisource' => [ 'page' => 104, 'index' => 106, ], 'sawikisource' => [ 'page' => 104, 'index' => 106, ], 'slwikisource' => [ 'page' => 100, 'index' => 104, ], 'svwikisource' => [ 'page' => 104, 'index' => 108, ], 'tewikisource' => [ 'page' => 104, 'index' => 106, ], 'vecwikisource' => [ 'page' => 102, 'index' => 104, ], 'viwikisource' => [ 'page' => 104, 'index' => 106, ], 'zhwikisource' => [ 'page' => 104, 'index' => 106, ], ],