Your template for Azure log forwarded is incomplete. You cannot deploy a working Azure Function if you do not deploy an App Plan with it, which has various parameters and environment variables required on the Azure Function based on the type of App Plan deployed (e.g. consumption, flex, etc.).

You have tests in this repository, are any of them actually validating it deploys (not just that it is valid syntax for ARM)?

The function_template for example doesn't include the web farm resource, so every deployment will get a conflict error like this (since it has no host to bring up the function app itself):

{
  "Code": "BadRequest",
  "Message": "Encountered an error (InternalServerError) from host runtime.",
  "Target": null,
  "Details": [
    {
      "Message": "Encountered an error (InternalServerError) from host runtime."
    },
    {
      "Code": "BadRequest"
    },
    {
      "ErrorEntity": {
        "Code": "BadRequest",
        "Message": "Encountered an error (InternalServerError) from host runtime."
      }
    }
  ],
  "Innererror": null
}