Next steps ()
I've had a proof of concept written in Swift for iOS put together for some time. I'm going to get working on an MVP (with collaboration and sharing) built on Cloudflare Workers. Ideally, Fleetbox will work on all major platforms (iOS, Android, Web).
I'm planning on splitting the project into two sections - the API and the frontends. The API will be a Cloudflare Worker storing data in Cloudflare D1 (for now, that might change as serverless database technology evolves). For frontends, I'll start with a web frontend written with SvelteKit deployed to Cloudflare Pages. That's the frontend framework I have the most experience with lately (this website is built with that stack!).
I'll be starting with using D1 for storage, though that doesn't have the best scalability or stability. It's a great system for getting a prototype made though. Since it's built on SQLite, it shouldn't be too much of a hassle to port to another SQL database in the future though.