When trying to trigger vibration through the Play Dynamic Force Feedback node, nothing happens on Android. I tested this on Windows as well with an Xbox Series X controller connected, and the vibration triggered as expected, so it may be specific to mobile.
Tested in //UE4/Release-4.26 @ CL 15973114 and this did not occur, so marking as a Regression.
No vibration occurs on the Android device
After a 2 second delay, the phone would start vibrating
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-126894 in the post.