Trying to deploy the Lambda splunk-logger function, I got the following error:
The runtime parameter of nodejs8.10 is no longer supported for creating or updating AWS Lambda functions. We recommend you use the new runtime (nodejs12.x) while creating or updating functions.
So it is impossible to use Lambda from the serverless app repository to get data into HEC. These templates should be removed.
I did find that in the "templates" section, there is a NodeJS 12.x version, but took me some (wasted) time to get there.