Does anyone here have recommendations for medication tracker/reminder apps? Opensource and either offline or self hosted strongly preferred.

@Janik Which platform?
On Android I really liked this one for being super simplistic: https://f-droid.org/en/packages/com.futsch1.medtimer/ (Kinda miss it on iOS now)
MedTimer: Med & Pill Reminder | F-Droid - Free and Open Source Android App Repository

Medication and pill reminder with log, fully offline and privacy focused