diff --git a/swh/loader/package/archive/loader.py b/swh/loader/package/archive/loader.py
--- a/swh/loader/package/archive/loader.py
+++ b/swh/loader/package/archive/loader.py
@@ -72,8 +72,8 @@
         url: str,
         artifacts: Sequence[Dict[str, Any]],
         extid_manifest_format: Optional[str] = None,
-        max_content_size: Optional[int] = None,
         snapshot_append: bool = False,
+        **kwargs: Any,
     ):
         f"""Loader constructor.
 
@@ -101,7 +101,7 @@
                 the new snapshot created by the loader
 
         """
-        super().__init__(storage=storage, url=url, max_content_size=max_content_size)
+        super().__init__(storage=storage, url=url, **kwargs)
         self.artifacts = artifacts  # assume order is enforced in the lister
         self.extid_manifest_format = (
             None
diff --git a/swh/loader/package/cran/loader.py b/swh/loader/package/cran/loader.py
--- a/swh/loader/package/cran/loader.py
+++ b/swh/loader/package/cran/loader.py
@@ -51,11 +51,7 @@
     visit_type = "cran"
 
     def __init__(
-        self,
-        storage: StorageInterface,
-        url: str,
-        artifacts: List[Dict],
-        max_content_size: Optional[int] = None,
+        self, storage: StorageInterface, url: str, artifacts: List[Dict], **kwargs: Any
     ):
         """Loader constructor.
 
@@ -64,7 +60,7 @@
             artifacts: List of associated artifact for the origin url
 
         """
-        super().__init__(storage=storage, url=url, max_content_size=max_content_size)
+        super().__init__(storage=storage, url=url, **kwargs)
         # explicit what we consider the artifact identity
         self.artifacts = artifacts
 
diff --git a/swh/loader/package/debian/loader.py b/swh/loader/package/debian/loader.py
--- a/swh/loader/package/debian/loader.py
+++ b/swh/loader/package/debian/loader.py
@@ -132,7 +132,7 @@
         storage: StorageInterface,
         url: str,
         packages: Mapping[str, Any],
-        max_content_size: Optional[int] = None,
+        **kwargs: Any,
     ):
         """Debian Loader implementation.
 
@@ -173,7 +173,7 @@
               }
 
         """
-        super().__init__(storage=storage, url=url, max_content_size=max_content_size)
+        super().__init__(storage=storage, url=url, **kwargs)
         self.packages = packages
 
     def get_versions(self) -> Sequence[str]:
diff --git a/swh/loader/package/deposit/loader.py b/swh/loader/package/deposit/loader.py
--- a/swh/loader/package/deposit/loader.py
+++ b/swh/loader/package/deposit/loader.py
@@ -107,8 +107,8 @@
         url: str,
         deposit_id: str,
         deposit_client: "ApiClient",
-        max_content_size: Optional[int] = None,
         default_filename: str = "archive.tar",
+        **kwargs: Any,
     ):
         """Constructor
 
@@ -118,7 +118,7 @@
             deposit_client: Deposit api client
 
         """
-        super().__init__(storage=storage, url=url, max_content_size=max_content_size)
+        super().__init__(storage=storage, url=url, **kwargs)
 
         self.deposit_id = deposit_id
         self.client = deposit_client
diff --git a/swh/loader/package/loader.py b/swh/loader/package/loader.py
--- a/swh/loader/package/loader.py
+++ b/swh/loader/package/loader.py
@@ -151,16 +151,7 @@
 
 
 class PackageLoader(BaseLoader, Generic[TPackageInfo]):
-    # Origin visit type (str) set by the loader
-    visit_type = ""
-    visit_date: datetime.datetime
-
-    def __init__(
-        self,
-        storage: StorageInterface,
-        url: str,
-        max_content_size: Optional[int] = None,
-    ):
+    def __init__(self, storage: StorageInterface, url: str, **kwargs: Any):
         """Loader's constructor. This raises exception if the minimal required
            configuration is missing (cf. fn:`check` method).
 
@@ -169,10 +160,7 @@
             url: Origin url to load data from
 
         """
-        super().__init__(
-            storage=storage, origin_url=url, max_content_size=max_content_size
-        )
-        self.visit_date = datetime.datetime.now(tz=datetime.timezone.utc)
+        super().__init__(storage=storage, origin_url=url, **kwargs)
 
     def get_versions(self) -> Sequence[str]:
         """Return the list of all published package versions.
diff --git a/swh/loader/package/maven/loader.py b/swh/loader/package/maven/loader.py
--- a/swh/loader/package/maven/loader.py
+++ b/swh/loader/package/maven/loader.py
@@ -8,7 +8,7 @@
 import logging
 from os import path
 import string
-from typing import Iterator, List, Optional, Sequence, Tuple
+from typing import Any, Iterator, List, Optional, Sequence, Tuple
 
 import attr
 import iso8601
@@ -110,7 +110,7 @@
         storage: StorageInterface,
         url: str,
         artifacts: Sequence[ArtifactDict],
-        max_content_size: Optional[int] = None,
+        **kwargs: Any,
     ):
         """Loader constructor.
 
@@ -123,7 +123,7 @@
             artifacts: List of single artifact information
 
         """
-        super().__init__(storage=storage, url=url, max_content_size=max_content_size)
+        super().__init__(storage=storage, url=url, **kwargs)
         self.artifacts = artifacts  # assume order is enforced in the lister
         self.version_artifact = {
             jar["version"]: jar for jar in artifacts if jar["version"]
diff --git a/swh/loader/package/nixguix/loader.py b/swh/loader/package/nixguix/loader.py
--- a/swh/loader/package/nixguix/loader.py
+++ b/swh/loader/package/nixguix/loader.py
@@ -75,9 +75,9 @@
         storage: StorageInterface,
         url: str,
         unsupported_file_extensions: List[str] = [],
-        max_content_size: Optional[int] = None,
+        **kwargs: Any,
     ):
-        super().__init__(storage=storage, url=url, max_content_size=max_content_size)
+        super().__init__(storage=storage, url=url, **kwargs)
         self.provider_url = url
         self.unsupported_file_extensions = unsupported_file_extensions
 
diff --git a/swh/loader/package/npm/loader.py b/swh/loader/package/npm/loader.py
--- a/swh/loader/package/npm/loader.py
+++ b/swh/loader/package/npm/loader.py
@@ -101,18 +101,13 @@
 
     visit_type = "npm"
 
-    def __init__(
-        self,
-        storage: StorageInterface,
-        url: str,
-        max_content_size: Optional[int] = None,
-    ):
+    def __init__(self, storage: StorageInterface, url: str, **kwargs: Any):
         """Constructor
 
         Args
             str: origin url (e.g. https://www.npmjs.com/package/<package-name>)
         """
-        super().__init__(storage=storage, url=url, max_content_size=max_content_size)
+        super().__init__(storage=storage, url=url, **kwargs)
         self.package_name = url.split("https://www.npmjs.com/package/")[1]
         safe_name = quote(self.package_name, safe="")
         self.provider_url = f"https://replicate.npmjs.com/{safe_name}/"
diff --git a/swh/loader/package/opam/loader.py b/swh/loader/package/opam/loader.py
--- a/swh/loader/package/opam/loader.py
+++ b/swh/loader/package/opam/loader.py
@@ -6,7 +6,7 @@
 import io
 import os
 from subprocess import PIPE, Popen, call
-from typing import Iterator, List, Optional, Tuple
+from typing import Any, Iterator, List, Optional, Tuple
 
 import attr
 
@@ -91,10 +91,10 @@
         opam_instance: str,
         opam_url: str,
         opam_package: str,
-        max_content_size: Optional[int] = None,
         initialize_opam_root: bool = False,
+        **kwargs: Any,
     ):
-        super().__init__(storage=storage, url=url, max_content_size=max_content_size)
+        super().__init__(storage=storage, url=url, **kwargs)
 
         self.opam_root = opam_root
         self.opam_instance = opam_instance
diff --git a/swh/loader/package/pypi/loader.py b/swh/loader/package/pypi/loader.py
--- a/swh/loader/package/pypi/loader.py
+++ b/swh/loader/package/pypi/loader.py
@@ -77,13 +77,8 @@
 
     visit_type = "pypi"
 
-    def __init__(
-        self,
-        storage: StorageInterface,
-        url: str,
-        max_content_size: Optional[int] = None,
-    ):
-        super().__init__(storage=storage, url=url, max_content_size=max_content_size)
+    def __init__(self, storage: StorageInterface, url: str, **kwargs):
+        super().__init__(storage=storage, url=url, **kwargs)
         self.provider_url = pypi_api_url(self.origin.url)
 
     @cached_method
diff --git a/swh/loader/package/tests/test_loader.py b/swh/loader/package/tests/test_loader.py
--- a/swh/loader/package/tests/test_loader.py
+++ b/swh/loader/package/tests/test_loader.py
@@ -54,6 +54,8 @@
 
 
 class StubPackageLoader(PackageLoader[StubPackageInfo]):
+    visit_type = "stub"
+
     def get_versions(self):
         return ["v1.0", "v2.0", "v3.0", "v4.0"]
 
diff --git a/swh/loader/package/tests/test_loader_metadata.py b/swh/loader/package/tests/test_loader_metadata.py
--- a/swh/loader/package/tests/test_loader_metadata.py
+++ b/swh/loader/package/tests/test_loader_metadata.py
@@ -88,6 +88,8 @@
 
 
 class MetadataTestLoader(PackageLoader[BasePackageInfo]):
+    visit_type = "metadata-test"
+
     def get_versions(self) -> Sequence[str]:
         return ["v1.0.0"]