This happened days after the One UI update. 1 week ago I got a black screen and did all the easy fixes I found on the web. It worked after 2 days. Then after a week, black screen again. Sound and vibration are still working. Alarms, sound notifications alike. I highly doubt that it's the screen or the battery. But all the technician will just automatically assume this. I never dropped it or was it wet. My battery is perfectly working. Find My Mobile can ring, detect wifi network and battery still. I was even able to remotely do a back up. Batt is still at 56%. Alarms keep on ringing as well.
I think Samsung should look into this rather having all A71 users replace their hardware.