Unable to download and install iOS 14.6 software update on my iPhone 11 despite many attempts

This support article by Apple might help you

https://support.apple.com/en-us/HT204204

May I try and help you?

Are you connected to Mobile Data or to Wi-Fi?

You will be able to download only if the following conditions are met:

• your iPhone must be plugged it to a power source
• your iPhone must be connected to Wi-Fi, not to Mobile/Cellular Data