diff --git a/services/docker-compose.yml b/services/docker-compose.yml
index ecb72a93469b..e7cf3774ca74 100644
--- a/services/docker-compose.yml
+++ b/services/docker-compose.yml
@@ -846,7 +846,6 @@ services:
       WEBSERVER_DB_LISTENER: ${WEBSERVER_DB_LISTENER}
       WEBSERVER_ANNOUNCEMENTS: ${WEBSERVER_ANNOUNCEMENTS}
       WEBSERVER_NOTIFICATIONS: ${WEBSERVER_NOTIFICATIONS}
-      WEBSERVER_CLUSTERS: ${WEBSERVER_CLUSTERS}
       WEBSERVER_FUNCTIONS: ${WEBSERVER_FUNCTIONS} # neede for front-end
       WEBSERVER_GROUPS: ${WEBSERVER_GROUPS}
       WEBSERVER_PRODUCTS: ${WEBSERVER_PRODUCTS}
@@ -955,7 +954,6 @@ services:
       WEBSERVER_ACTIVITY: ${WB_DB_EL_ACTIVITY}
       WEBSERVER_ANNOUNCEMENTS: ${WB_DB_EL_ANNOUNCEMENTS}
       WEBSERVER_CATALOG: ${WB_DB_EL_CATALOG}
-      WEBSERVER_CLUSTERS: ${WB_DB_EL_CLUSTERS}
       WEBSERVER_DB_LISTENER: ${WB_DB_EL_DB_LISTENER}
       WEBSERVER_DIAGNOSTICS: ${WB_DB_EL_DIAGNOSTICS}
       WEBSERVER_EMAIL: ${WB_DB_EL_EMAIL}
@@ -1068,7 +1066,6 @@ services:
       WEBSERVER_ACTIVITY: ${WB_GC_ACTIVITY}
       WEBSERVER_ANNOUNCEMENTS: ${WB_GC_ANNOUNCEMENTS}
       WEBSERVER_CATALOG: ${WB_GC_CATALOG}
-      WEBSERVER_CLUSTERS: ${WB_GC_CLUSTERS}
       WEBSERVER_DB_LISTENER: ${WB_GC_DB_LISTENER}
       WEBSERVER_DIAGNOSTICS: ${WB_GC_DIAGNOSTICS}
       WEBSERVER_EMAIL: ${WB_GC_EMAIL}
diff --git a/services/web/server/src/simcore_service_webserver/users/_controller/rest/_rest_schemas.py b/services/web/server/src/simcore_service_webserver/users/_controller/rest/_rest_schemas.py
index df300668caca..ae46ed501d75 100644
--- a/services/web/server/src/simcore_service_webserver/users/_controller/rest/_rest_schemas.py
+++ b/services/web/server/src/simcore_service_webserver/users/_controller/rest/_rest_schemas.py
@@ -14,7 +14,9 @@
 from models_library.api_schemas_webserver._base import InputSchema
 from models_library.api_schemas_webserver.users import UserAccountGet
 from models_library.emails import LowerCaseEmailStr
+from models_library.utils.common_validators import empty_str_to_none_pre_validator
 from pydantic import (
+    BeforeValidator,
     ConfigDict,
     Field,
     StringConstraints,
@@ -64,7 +66,9 @@ class UserAccountRestPreRegister(InputSchema):
     institution: Annotated[
         str | None, Field(description="company, university, ...")
     ] = None
-    phone: PhoneNumberStr | None
+    phone: Annotated[
+        PhoneNumberStr | None, BeforeValidator(empty_str_to_none_pre_validator)
+    ]
 
     # billing details
     address: str
diff --git a/services/web/server/tests/unit/isolated/test_studies_dispatcher_projects_permalinks.py b/services/web/server/tests/unit/isolated/test_studies_dispatcher_projects_permalinks.py
index 9a182352efad..def692faeccd 100644
--- a/services/web/server/tests/unit/isolated/test_studies_dispatcher_projects_permalinks.py
+++ b/services/web/server/tests/unit/isolated/test_studies_dispatcher_projects_permalinks.py
@@ -39,7 +39,6 @@ def app_environment(
             **env_devel_dict,
             "WEBSERVER_ACTIVITY": "null",
             "WEBSERVER_CATALOG": "null",
-            "WEBSERVER_CLUSTERS": "false",
             "WEBSERVER_NOTIFICATIONS": "0",
             "WEBSERVER_DIAGNOSTICS": "null",
             "WEBSERVER_DIRECTOR_V2": "null",
diff --git a/services/web/server/tests/unit/with_dbs/01/test_groups_handlers_classifers.py b/services/web/server/tests/unit/with_dbs/01/test_groups_handlers_classifers.py
index 02a0ddf581ba..7fd721eb446f 100644
--- a/services/web/server/tests/unit/with_dbs/01/test_groups_handlers_classifers.py
+++ b/services/web/server/tests/unit/with_dbs/01/test_groups_handlers_classifers.py
@@ -27,7 +27,6 @@ def app_environment(
             # exclude
             "WEBSERVER_ACTIVITY": "null",
             "WEBSERVER_CATALOG": "null",
-            "WEBSERVER_CLUSTERS": "null",
             "WEBSERVER_COMPUTATION": "null",
             "WEBSERVER_DIAGNOSTICS": "null",
             "WEBSERVER_EMAIL": "null",
diff --git a/services/web/server/tests/unit/with_dbs/03/test__openapi_specs.py b/services/web/server/tests/unit/with_dbs/03/test__openapi_specs.py
index 886817bbf263..d3b561cae319 100644
--- a/services/web/server/tests/unit/with_dbs/03/test__openapi_specs.py
+++ b/services/web/server/tests/unit/with_dbs/03/test__openapi_specs.py
@@ -41,7 +41,6 @@ def app_environment(
             "WEBSERVER_GARBAGE_COLLECTOR": "null",
             # enable plugins that by default are disabled
             "WEBSERVER_DEV_FEATURES_ENABLED": "1",
-            "WEBSERVER_CLUSTERS": "1",
             # enables activity WEBSERVER_ACTIVITY
             "PROMETHEUS_URL": f"https://{faker.domain_name()}",
             "PROMETHEUS_USERNAME": faker.user_name(),