Ensure subscribe button appears only on relevant models

netbox/templates/generic/object.html

@@ -77,7 +77,7 @@ Context:
       {% if perms.extras.add_bookmark and object.bookmarks %}
         {% bookmark_button object %}
       {% endif %}
-      {% if perms.extras.add_subscription %}
+      {% if perms.extras.add_subscription and object.subscriptions %}
         {% subscribe_button object %}
       {% endif %}
       {% if request.user|can_add:object %}

netbox/utilities/templates/buttons/subscribe.html

@@ -1,16 +1,18 @@
 {% load i18n %}
-<form action="{{ form_url }}?return_url={{ return_url }}" method="post">
-  {% csrf_token %}
-  {% for field, value in form_data.items %}
-    <input type="hidden" name="{{ field }}" value="{{ value }}" />
-  {% endfor %}
-  {% if subscription %}
-    <button type="submit" class="btn btn-cyan">
-      <i class="mdi mdi-bell-minus"></i> {% trans "Unsubscribe" %}
-    </button>
-  {% else %}
-    <button type="submit" class="btn btn-cyan">
-      <i class="mdi mdi-bell-plus"></i> {% trans "Subscribe" %}
-    </button>
-  {% endif %}
-</form>
+{% if form_url %}
+  <form action="{{ form_url }}?return_url={{ return_url }}" method="post">
+    {% csrf_token %}
+    {% for field, value in form_data.items %}
+      <input type="hidden" name="{{ field }}" value="{{ value }}" />
+    {% endfor %}
+    {% if subscription %}
+      <button type="submit" class="btn btn-cyan">
+        <i class="mdi mdi-bell-minus"></i> {% trans "Unsubscribe" %}
+      </button>
+    {% else %}
+      <button type="submit" class="btn btn-cyan">
+        <i class="mdi mdi-bell-plus"></i> {% trans "Subscribe" %}
+      </button>
+    {% endif %}
+  </form>
+{% endif %}

netbox/utilities/templatetags/buttons.py

@@ -4,6 +4,7 @@ from django.urls import NoReverseMatch, reverse
 
 from core.models import ObjectType
 from extras.models import Bookmark, ExportTemplate, Subscription
+from netbox.models.features import NotificationsMixin
 from utilities.querydict import prepare_cloned_fields
 from utilities.views import get_viewname
 
@@ -97,6 +98,10 @@ def delete_button(instance):
 
 @register.inclusion_tag('buttons/subscribe.html', takes_context=True)
 def subscribe_button(context, instance):
+    # Skip for objects which don't support notifications
+    if not (issubclass(instance.__class__, NotificationsMixin)):
+        return {}
+
     # Check if this user has already subscribed to the object
     content_type = ContentType.objects.get_for_model(instance)
     subscription = Subscription.objects.filter(