App for what? What are you using that doesn't already have a clock?

I use this: https://www.f-droid.org/packages/com.best.deskclock/

The funniest answer I saw to the question of the most privacy respecting clock was "a sundial", but thats just my childish sense of humour.

Depending on what you want, a clock app is something you can easily build yourself. Nothing more private than what is already yours.

I like Clock You.

Hi guys, thanks for yur help. With "Simple clock" and "clock you" the problem is that when I turn my screen off, the alarm doesnt work. I don't understand cause I unabled all authorisation possible with these apps. How can I solve it ? My phone is a TCL with Android 11.

You could try this https://www.f-droid.org/en/packages/com.simplemobiletools.clock/

iOS: Clocks

Android: Simple Clock

Linux: GNOME Clocks