How can I check if an object has entered a trigger with a script attached to a different object?

Excellent! Worked perfect! Thank you so much!

Thanks, helped a lot ^_^

And for more accurate, you can also create a variable for the object generating the collision

 public class Player : MonoBehaviour
  {
      public bool EnteredTrigger;
      public GameObject CollisionWith;  
  
      public void OnTriggerEnter(Collider other)
      {
          if (other.tag == /*the tag*/)
              EnteredTrigger = true;
              CollisionWith = other.gameObject;
      }
  }     
  public class OtherScript : MonoBehaviour
  {
      private GameObject m_Player;
      private void Start()
      {
          m_Player = GameObject.FindWithTag("Player");
      }     
      private void Update()
      {
          if (m_Player.GetComponent<Player>().EnteredTrigger)
              { 
              //Do whatever
               }
      }
  }