> You can easily download a multi-hour recording of, say, a waterfall, and just play it from your device.
That's the thing, you can't, not easily. On mobile—especially iOS—it's frustratingly difficult to transfer and use normal files without an associated app.
Sounds like what it was like to use an iPad to organize files, before the Files app in 2017(!)
On Android, I use a YT client app to download a 320kbps M4A of the white noise file, and then play it on anything I want...music app, podcast app, audiobook app...they all work, just like they would on a computer
I just went and checked. By default extensions are hidden and can't be changed. If you hit the menu thing and select "Show all extensions" you can now edit file extensions.
Seems appropriate to me. Changing a files extension is pretty unusual and will break things in ways users don't understand. But if you do know what you are doing, it took me 20 seconds to work out how to do it without reading a manual.
On iOS, the "generic" music app became Apple Music. It is possible to use a local library but I suspect many/most people don't even know that, Apple really pushes you towards their subscription streaming service.
That's the thing, you can't, not easily. On mobile—especially iOS—it's frustratingly difficult to transfer and use normal files without an associated app.