Apple clock replacement app
Recommend a Clock app to replace Apple clock, which is not working properly under iOS 26
iPhone 15 Pro, iOS 26
As no one here knows 1) what your preferences are and 2) what problem you're having with the Apple Clock, it's almost impossible to make such a recommendation.
I suggest you search for "clock" in the App Store, look for the ones with good ratings, then read the reviews. Be sure to set the sort order on the reviews to "Recent."