lets try this

LightlessSyncServer/LightlessSyncShared/Migrations/20251019163402_AddAndChangeTagsUserGroupProfile.cs

@@ -16,7 +16,9 @@ namespace LightlessSyncServer.Migrations
                 type: "integer[]",
                 nullable: true);
 
-            migrationBuilder.Sql("UPDATE group_profiles SET tags = NULL;");
+            migrationBuilder.Sql(
+                "ALTER TABLE group_profiles ALTER COLUMN tags TYPE integer[] USING string_to_array(tags, ',')::integer[];"
+            );
 
             migrationBuilder.AlterColumn<int[]>(
                 name: "tags",