This is not an alternative way of using selenium. It's a way to avoid using selenium. The advantage over selenium is that tests and application code are run in the same process, so they tend to be faster, less brittle and easier to debug. The downside is that they are not cross-browser.
Yes you can use it to describe and automate systems built in other technologies and I've done that on a couple of projects. It's a good fit for any web app with a lot of client-side code. But its sweet spot is definitely node.js apps.
You could certainly use electron as a driver for tests written in other tech, but there is no capybara electron driver that I'm aware of. Using cucumber-electron means you write your step definitions (automation code) in JavaScript.