I'll recommend ruby for backend, because it's very stable, fast to develop and in general follows consolidated patterns, when I need to see some open source code or see someone else code, it feels more natural, because the developers normally guarantee the code organization, better practices and code coverage with tests (obviously there are many untested libraries and projects out there), maybe give a try to hanami (it's on my to-do list to study), although my knowledge is more deep about rails.
About frontend I liked a lot react, I'm very comfortable with it, the two major downsides are many libs doesn't follow semver practice (and a minor patch could potentially brake your application, but this issue occur with many javascript libs) and another there isn't a structure pattern, some devs like to use domain driven structure.