And what's Ruby's maintainability like? As in, once the project gets inherited by a new dev, or your reach a larger than a couple of devs scale?

Not being ironic, genuinely curious. My only parallel is JavaScript and that becomes a pain in the ass quick due to the small bugs that go unnoticed, even working as a lone dev. TypeScript catches a great deal of those and you can get by with less testing and a more readable (imo) codebase, so a win-win for me.