Front-end dev wanting to move into shopify work, where to start?

Once you've got two or three custom sections you're happy with, put them in a demo store and use that as your portfolio. Small fixes and section builds for existing stores are the easiest first paid jobs, way easier to land than a full theme. And run Lighthouse on everything you build. Merchants care a lot about speed and a heavy section is the first thing they'll blame.

You're already most of the way there. Shopify themes are HTML, CSS and JS plus Liquid, their templating language, which you'll pick up in a few days. What I'd do: 1. Make a free Partner account, it lets you spin up development stores. 2. Install the Shopify CLI and pull down Dawn, the default theme. Read how sections, blocks and the JSON templates fit together, that's the core of modern themes. 3. Build a couple of custom sections merchants can edit from the theme editor. That's what most paid small jobs are. The bit that trips front-end people up is that merchants edit everything in the customizer, so build things to be configurable, not hardcoded. Once you're comfortable, look at app work and the Storefront API if you want to go headless.