The Identifier Validator Plugins in AvailablePlugin use a singular $name in their Controllers, which results in the use of singular View files instead of the standard plural pattern.

eg, in AvailablePlugin/RegexIdentifierValidator/Controller/RegexIdentifierValidatorsController.php:

public $name = "RegexIdentifierValidator";

which implies AvailablePlugin/RegexIdentifierValidator/View/RegexIdentifierValidator instead of AvailablePlugin/RegexIdentifierValidator/View/RegexIdentifierValidators. Switch this to plural and check for other plugins (and other types of plugins) where this may have happened.