So I made Ambi, a small iOS app with a clean interface and a set of freely available ambient sounds — rain, waves, wind, birds, that sort of thing. You can mix them, adjust volume levels, and just let it play all night or while you work. Everything works offline and there are no hidden catches.
It’s something I built for myself first, but I figured others might find it useful too. Feedback, bugs, and suggestions are all welcome.
https://apps.apple.com/app/ambi-white-noise-sleep-sounds/id6...
iOS Settings - Accessibility - Audio & Visual - Background Sounds
Offers the same as OP's app, except mixing. The only thing I miss is a a fade out possibility. For example, set timer at 01:00 minute and it slowly fades out over that whole minute. Much better than such an abrupt end. Not sure if OP's app does offer that.