https://f-droid.org/en/packages/com.sesu8642.infusion_timer/
Enthusiast Tea Timer | F-Droid - Free and Open Source Android App Repository
Tea timer for Gong Fu and western style brewing for true enthusiasts.
timer f droidopen sourcetea
https://f-droid.org/en/packages/dev.randombits.intervaltimer/
Interval Timer | F-Droid - Free and Open Source Android App Repository
The simplest interval timer you can imagine
timer f droidopen sourcefree