update: now player uses additional collider to detect ground

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;
+    }
+}