You have jsreport custom scripts where you can do everything you want.
There is normal nodejs that should be able to do react server side rendering.
You can, for example, load an asset with react component and render it in the script.
You can also send to jsreport just html and do the html rendering in your system.
Or even send just an url to the hosted page.
It is fully up to you and your imagination. :) jsreport shouldn't be the limitation.