How to enable developer mode on an iPhone or iPad ( iOS | iPadOS )?

I got an alert when tried to open one provisioned testing build on iOS 16.0. Alert says -

"Your App" required Developer Mode to run. Until Developer Mode has been enabled this app will not be available for use.

In Short

Settings -> Privacy & Security -> Developer Mode -> turn ON Developer mode

In some cases you may have to unplug iOS device from Mac and re-plug it to see the "Developer Mode" option.

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In Depth

In iOS 16.0 Apple have made turning Developer Mode On mandatory if you want to physically connect your device to Xcode on Mac.

When you attempt to build and run to the device, Xcode displays following alert to tell you the destination isn’t valid because Developer Mode is disabled.

To Enable developer mode on iPhone

Settings -> Privacy & Security -> Developer Mode -> turn ON Developer mode as follows :

1. In Settings app on iPhone, select Privacy & Security.

2. Scroll down to the Developer Mode. Turn on it.

3. After that, choose Restart from action sheet to restart your iPhone.

4. A pop-up window appears when the phone is rebooted. To enable developer mode, click "Turn On" again and then enter the device password.

Ref - Apple Doc - Enabling Developer Mode on a device