Completing a Web Form as an Action

I want to fill out a single page web form (fill text into IDs and click() a submit button) when an action runs. I know this is borderline out of scope, but I'm hoping someone has figured this out. So far I've thought of two ways to go about this, but I have significant gaps in each.

Method 1
Use an automation and testing tool to fill out the form. Have this run on a machine (cloud, desktop, Pi - doesn't matter to me) when a Hubitat rule fires a webhook.
The gap here is that I am not aware of an automation tool (at least a free one) that will run an automation based on receiving a webhook.

Method 2
Actually have a Hubitat app load the URL containing the form, and use Xpath or JS to fill out the form.

The second method is WAY more simple and sleek, but I've zero idea how to make an app, whether this would be possible, etc. I have experience doing basic front end web, some SQL, etc - never done anything like that. If there is an app that I've not found that can get me close, perhaps I can tweak from there.

Any ideas?

This could maybe be done with a custom app.

Can maybe look at Event ghost for this.