update: now player uses additional collider to detect ground

Assets/Prefabs/Player.prefab

@@ -1,5 +1,71 @@
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Assets/Scripts/Player/GroundDetector.cs

@@ -0,0 +1,14 @@
+using UnityEngine;
+
+public class GroundDetector : MonoBehaviour
+{
+    public bool onGround { get; private set; } = false;
+
+    void OnTriggerEnter(Collider other) {
+        if (other.CompareTag("Ground")) onGround = true;
+    }
+    void OnTriggerStay(Collider other) { OnTriggerEnter(other); }
+    void OnTriggerExit(Collider other) {
+        if (other.CompareTag("Ground")) onGround = false;
+    }
+}

Assets/Scripts/Player/GroundDetector.cs.meta

@@ -0,0 +1,2 @@
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Assets/Scripts/Player/PlayerMovement.cs

@@ -17,16 +17,18 @@ public class PlayerMovement : MonoBehaviour
     [Header("Debug info")]
     [SerializeField] bool isCrouching = false;
     [SerializeField] Vector3 gravityVelocity;
-    [SerializeField] bool grounded;
+    [SerializeField] bool grounded = false;
 
     CharacterController characterController;
+    GroundDetector ground;
 
     void Start() {
         characterController = GetComponent<CharacterController>();
+        ground = GetComponent<GroundDetector>();
     }
 
     void Update() {
-        grounded = GetOnGround();
+        grounded = ground.onGround;
         HandleCrouching();
         HandleMovement();
         HandleJumping();
@@ -69,10 +71,6 @@ public class PlayerMovement : MonoBehaviour
         characterController.Move(gravityVelocity * (Time.deltaTime * gravityMultiplier));
     }
 
-    bool GetOnGround() {
-        return Physics.CheckSphere(legsPosition.position, legsRadius, groundMask);
-    }
-
     void OnControllerColliderHit(ControllerColliderHit hit) {
         hit.gameObject.SendMessage("ReverseOnControllerColliderHit", hit, SendMessageOptions.DontRequireReceiver);
     }