There's not a broad repo of software other than the app store, but see my other comment: Sonos distributes a prior version of their controller via their own web

There's not a broad repo of software other than the app store, but see my other comment: Sonos distributes a prior version of their controller via their own web site. You download it from there, but you have to give the "okay" in the security settings to trust it before it'll work. Another example is Blink.io, which is currently the best terminal emulator for iOS. (It works GREAT, btw -- I can use emacs and orgmode in it, even.) Blink is in the app store, at $19.99, but you can also download and build from source and get it on your device that way. That's more trouble than most folks will go to, but my assumption is that it's not too high a bar for most folks who are seriously sideloading software on Android.