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And can also set a timer for 6 hrs. Downside, will need to start the timer manually.

There are apps out there that do this, just have not looked at them myself (I go the alarms route).

Can setup 6 repeating Reminders in Reminders (daily at hh:mm, hh+6, hh+12).
 
I’ve been trying to do something similar. The least cumbersome solution and the one that worked best for me, was resurrecting an app I’d used previously - Streaks.
 
I now have 4 alarms that will repeat for seven days. It ain't perfect, but it will work without costing anything more.
 
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