Premium upgrade is worthwhile
However, a solution is to upgrade to the premium version with a one-time purchase of $6 (in year 2024), which eliminates the ads. To me, this is a small price to pay for quality software.
This program is very good; it's just the sort of replacement for which I was looking. (After having upgraded my old iPhone to a new model, I then discovered that my old third-party clock application was no longer available.)
By the way, after noticing that this new (to me) "The Clocks" program permits the dimming or brightening of the display, but does so in an uneven fashion, there is a built-in solution . It's to change the setting called "Brightness Control" from "Hardware" to "Software". Then the process of swiping to dim or brighten becomes smooth (rather than jerky).
Thanks for the nice application.