Magento 2.3.4 patch for the `"telephone" is required. Enter and try again.` error. https://devdocs.magento.com/guides/v2.3/release-notes/release-notes-2-3-5-open-source.html#eav

MC29999_TelephoneOptionalRequired.patch

--- Model/Config.php	2020-04-23 08:56:42.000000000 +0200
+++ Model/Config.php	2020-05-15 16:28:16.337488649 +0200
@@ -822,6 +822,10 @@
             $fullAttributeData = array_key_exists('is_required', $attributeData);

             if ($existsFullAttribute || (!$existsFullAttribute && !$fullAttributeData)) {
+                $scopeIsRequired = $attributeData['scope_is_required'] ?? null;
+                if ($scopeIsRequired !== null) {
+                    $attribute->setData('scope_is_required', $scopeIsRequired);
+                }
                 return $attribute;
             }
         }