Doesn’t that require you to host it and have it available on the open web, though? Is there a host that allows you to, for free, not only HTML/CSS/JS but also access to arbitrary tools and bespoke scripts on the backend?
As a lark, I built a set of personal productivity apps that are delivered as standalone local webpages. Works surprisingly well on Android, haven't tested on iOS.
Yeah it stands for Progressive Web App - but there are lots of hosting solutions with generous free tiers.
I host a bunch of my own PWAs on Cloudflare using Pages and Workers. It's been free so far.
For free? No, but if you built a native app that needed a backend, you'd still need to host the backend somewhere too. I host my own web apps from a cheap mini pc at home and access them over tailscale for personal use.