🐛 | Field CSS | [PHP 8.1] Deprecated function: Calling static trait method Drupal\field_css\Traits\CssTrait::itemPrefixes
You have absurdly over engineered this fix. You can still use static methods on traits. A trait is a list of methods that are "merged" (possibly to various classes) which "use" the trait. Once using a trait, the class now have all those trait's methods as methods of its own. Just call them using "self::method()" instead "trait::method()" and you are good to go.