I would also like to use Joplin for my reminders. Except currently the App does not trigger a callback.
I was initially thinking about an authorization problem, but the 3 authorizations are present.
That's right, I didn't look much, sorry 
With or without Don't Disturb mode, nothing happens.
I'm on Android 8.0.
Even if you set a reminder for 3 mn laters ?
On the same task ? Or on an another ?
if you define a reminder for 15:25 today ; this will work ?
Aie ! I missed your message.
Why this particular time?
I can try 15:30.
My first question is:
are you able to trigger a reminder if you set it for the current hour + 3minutes ?
No, nothing happens.
It works for you ? If yes, Android 8.0 ?
this behavior works for me on android 7.1.1
but not always when a reminder is set, very later (later the same day or the day after or month after), and worst when the “do no distrub” feature is enable.