I updated my iOS 13 last night and now the camera isn’t working

Try a simple reboot:

Tap and quickly release volume up button

Tap and quickly release volume down button

Press and keep holding the power button (keep holding past swipe to power off) until the Apple Logo appears, then let go.

This worked for another user yesterday

When you're in the camera app, turn on airplane mode and close the app on the multitask manager. Then, turn off airplane mode and open the camera app.

I know this seems like a dumb fix, it may or may not work for you. However, it did for me.

I don't recommend anyone to update to ios 13.0 or 13.1 right now because it is honestly a joke. I restored my phone 3 times and tried to downgrade my phone until i found this fix.

I have the same issue on my iPhone 8 since roughly a month (so must be since iOS 12.3.1?). I hoped that iOS 13 would make it better but in fact it’s worse now. Also after installing 13.1.2 which according to Apple should fix camera Issues, it’s still black. All describes solutions here are not helping. It sometimes works but most of the time not. I already had a session with Apple support last week and the hardware seems to be fine. So Apple, when will this be fixed. A smartphone without camera is pretty ******...

Try to restore it to factory settings and see how it goes.

Restore your iPhone, iPad, or iPod to factory settings - Apple Support

Next option would be restore from backup. This link explains how --> Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

Have you recently dropped the device or got it wet?

Same issue here. iPhone 8+, upgraded unintentionally to iOS 13.1.2, camera app is all black. Tried the fixes above with no luck. Happy for any advice.