We are sorry to hear about your experience with the recent updates on your Samsung Galaxy A71 having issues with a total black screen. I feel and understand it, expecting my device to be better after an update. If I encounter similar experience, I will be bothered too.
There is no better way but to submit your device to Samsung Authorized Service Center in order to have it assess and pinpoint the root cause of the issue.
Should you need further assistance and guidance, you may contact us via our online Samsung Customer Care support channels below.