Do not offer to create a new customer account if a membership is required

src/pretix/presale/checkoutflow.py

@@ -254,6 +254,14 @@ class CustomerStep(QuestionsViewMixin, CartMixin, TemplateFlowStep):
             field.widget.is_required = False
         return f
 
+    @cached_property
+    def signup_allowed(self):
+        return not any(
+            p.item.require_membership or
+            (p.variation and p.variation.require_membership)
+            for p in self.positions
+        )
+
     @cached_property
     def guest_allowed(self):
         return not any(
@@ -330,6 +338,7 @@ class CustomerStep(QuestionsViewMixin, CartMixin, TemplateFlowStep):
             self.cart_session.get('customer_mode', 'login' if self.request.customer else '')
         )
         ctx['guest_allowed'] = self.guest_allowed
+        ctx['signup_allowed'] = self.signup_allowed
 
         if 'customer' in self.cart_session:
             try: