Yes, it is more tricky. Just for your the future needs... you have two options:

Add to script something like this

function beforeRender(req, res) {
    console.log(JSOn.stringify(req))
}

And check jsreport console output or logs. It will be written there with debug level.

Write serialized request to the request template content and it will be printed in your report.

function beforeRender(req, res) {
    req.template.content = JSON.stringify(req)
}

Please share playground demo.

It is just a guess but...
It seems something is cleaning input req.data where xlsx is storing parsed document. Maybe a custom script.
Make sure you always extend the input data instead of assigning it.

function beforeRender(req, res) {
  req.data = Object.assign({}, req.data, {foo: "foo"})
}

Try to check the req parameter in the scripts beforeRender.
You find there req.options.scheduling.schedule which I believe solves your problem.

Does it fail also for a hello world template? It can be an error specific to your template.

Chrome in docker requires extra installation. Check what we do in the base image
https://github.com/jsreport/jsreport/blob/master/docker/full/Dockerfile

Theoretically, it could work as you have it, but maybe there is a problem with merging config
ENV chrome_launchOptions_executablePath google-chrome-stable
Try to check if this env is set in the container. If not, try to set it in your config.

No, you need to spin your own instance and update jsreport-chrome-pdf extension to the latest version
npm i jsreport-chrome-pdf@1.5.0

The mentioned example is downloading html, explicitly setting html base tag and let it evaluate by chrome.
In normal cases, this is enough. The js and styles are properly evaluated.

Unfortunately, this breaks for the previously linked angular apps, because they are behind github web server that sends X-Content-Type-Options: nosnif headers and doesn't allow us to do this trick. However, normally it should work as mentioned.

Try to check out this
https://jsreport.net/learn/chrome-pdf#printing-triggers

jsreport can fetch a URL using the custom script and print it.
You can try to fiddle with this demo and your pages.
https://playground.jsreport.net/w/jan_blaha/oLkDCYZ9