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.
I've gotten used to having my rails application (server) running in the same thread as my cucumber (client-side) steps, thanks to cucumber-rails. So I could see why this would be especially useful for testing node.js applications, with the same advantages. (A fault detected anywhere on either side of the test execution, client or server, can be escalated and reported to stop the entire test, delivering a really good, clear idea of where to look in the code for the violator!)
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.
(I'm the author of cucumber-electron)