Trigger when record has updated after chatter post through feeditem class to GROUP ID OR MENTIONS

A MAIN GOAL : TO ALARM ON EACH USERS IN A GROUP FOR RECORD UPDATE (NO PLATFORM EVENTS) API 44 or higher

Hello i want to post a article to chatter group members, but i tried to put group id to the parent Id it doesn't work. i know it is inappropriate to put a group id to Field name 'ParentId' but i did some google it, and some people said it is possible..

I have tried to use List of set ID, iterate it and put ids to the ParentId. It was possible to mention each user, but it keeps iterate unnecessarily until the number of user to chatter post..

        for(Id userids  : groupwithUser){
            FeedItem post = new FeedItem();
            //post.ParentId = userids; // RecordId                    
            post.ParentId = groupIds; // group Id                    
            post.Body = status;
            listChangedField.add(post);
            system.debug('listChangedField :'+listChangedField);
        }

Any suggestion to post a group Id or mention each users at once?(not until the iterate all list of users) Thank you in advance.

Error message if i put an GroupID on ParentID. ERROR MESSAGE : System.DmlException: Insert failed. First exception on row 0; first error: FIELD_INTEGRITY_EXCEPTION, Parent ID: id value of incorrect type: