Yes, React.NET is not maintained anymore so I wouldn't go this road. I didn't get fully what you are trying to do - is Opti CMS the master source for the content? Or you are trying to pull content from a different source to Opti CMS?

Thanks for the reply Bartosz.

Opti is neither the source of the raw content or its UI code.  We want to wrap a React widget inside a block or page.  The vendor's devs noted that it would not be simple to pull in these widgets to a ASP.NET project.

Hi
Not sure if this answers you question but this is what I do when I need React in MVC website.

• The index.cshtml for this block should be something like this

<div id="some_unique_name"></div>

• then you include all the scripts generated by your React app to the page (either globally or just in this view)
• then you need some code to initialize the React 

const domNode = document.getElementById('some_unique_name');
const root = createRoot(domNode);
root.render(<YourReactComponent />);

As a result separate React App will be rendered wherever you put this block.

This is also described here: https://react.dev/learn/add-react-to-an-existing-project

You could use something like React Abode (which replaced the excellent React Habitat) - https://github.com/labd/react-abode (It's not been touched for a while, but should do the job)

Also check out https://github.com/DaniilSokolyuk/NodeReact.NET but might be overkill for a single react island

https://github.com/DaniilSokolyuk/NodeReact.NET looks very promising but they do not have on the fly jsx to js so you would still have to configure transpilation/bundling etc. but probably if you have those react widgets library then you must have some kind build/test tools for those right? What is that widget library you mentioned? Is that an npm package or you were just given source code or dist?