It's deprecated now to not manifest_version have set in extension.json
" Use of WikiSEO's extension.json or skin.json does not have manifest_version was deprecated in MediaWiki 1.29. [Called from ExtensionRegistry::loadFromQueue in /srv/mediawiki/w/includes/registration/ExtensionRegistry.php at line 161]"
It's deprecated now to not manifest_version have set in extension.json
" Use of WikiSEO's extension.json or skin.json does not have manifest_version was deprecated in MediaWiki 1.29. [Called from ExtensionRegistry::loadFromQueue in /srv/mediawiki/w/includes/registration/ExtensionRegistry.php at line 161]"