Similar to how things were done in airbytehq/airbyte#9163

overrite config if sequence of 2 characters '\' an 't' is found in the delimeter config, then convert it into a \t [TAB] character. Then, proceed with standard validation

airbyte-integrations/connectors/source-s3/source_s3/v4/source.py

@@ -27,6 +27,8 @@ def read_config(self, config_path: str) -> Mapping[str, Any]:
         validate the config against the new spec.
         """
         config = super().read_config(config_path)
+        if config.get("format", {}).get("delimiter") == r"\t":
+            config["format"]["delimiter"] = "\t"
         if not self._is_v4_config(config):
             parsed_legacy_config = SourceS3Spec(**config)
             converted_config = LegacyConfigTransformer.convert(parsed_legacy_config)