I built something similar for personal use. It's a Mac app that uses AppleScript to poll Spotify for the track that is currently playing. It then looks for chords on Ultimate Guitar through a small NodeJS API that uses Puppeteer to scrape the site. I'll usually just put my guitar playlist on shuffle and have this app open alongside it.
We worked with Primephonic on the development of the platform, and this was one of the topics that got a lot of attention. In this talk about the app architecture [1] a former team mate touches upon the datamodel briefly.