You are supposed to download the DXB app but if you enter a foreign number you may not get an alert once your results are ready. If you do get an alert it may be delayed.
Pure Health conduct the tests at DXB. Download the purehealth.ae app as well. It updates as soon as your results are ready bit you need to login to check. In my experience it updates much quicker as it gave me the all clear after circa 12 hours each time whilst the DXB app had still not updated.
My last trip to DXB was in late Feb so the DXB app may have improved since.