Uncheat-able iOS Break Timer

When I’m using my computer devices (Mac, iPad, iPhone) I tend to sit in one spot too long.

For macOS, I use Dejal Software’s Time Out utility: every 48 minutes it blanks the screen and locks out the keyboard. Even if I reboot, it ensures I take that 12-minute break (that's just an example: you can define any break schedule you like). I want the same solution for my iPhone and iPad.

The App Store offers scores of Pomodoro timers, but they just send a notification. As far as I can tell, the system tools — Focus and ScreenTime — aren’t restrictive enough. I’m not a programmer, so advising me to "write a shortcut" won’t help. Does what I want exist? Or do you know someone who could create it?