Poor Man's Back End-as-a-Service (BaaS), Similar to Firebase/Supabase/Pocketbase

Do we still need a back-end, now that Chrome supports the File System Access API on both desktop and mobile?

I have started writing web apps that simply store the user data as a file, and I am very pleased with this approach.

It works perfectly for Desktop and Android.

iOS does not allow for real Chrome everywhere (only in Europe, I think), so I also offer to store the data in the "Origin private file system" which all browsers support. Fortunately it has the same API, so implementing it was no additional work. Only downside is that it cannot put files in a user selected directory. So in that mode, I support a backup via an old-fashioned download link.

This way, users do not have to put their data into the cloud. It all stays on their own device.

At least on the Android front, I'd prefer the app allow me to write to my own storage target. The reason is because I already use Syncthing-Fork to monitor a parent Sync directory of stuff (Obsidian, OpenTracks, etc.) and send to my backup system. In effect it allows apps to be local first and potentially even without network access, but allow me to have automatic backups.

If there were something that formalized this a little more, developers could even make their apps in a... Bring Your Own Network... kinda way. Maybe there's already someone doing this?