Since discovering the problem since updating your iPad, have you performed a forced-restart of your iPad? A restart will often clear an isolated or post-update software issue:
Force restart iPad (models with Face ID or with Touch ID in the top button)
If your iPad doesn’t have the Home button, do the following:
- Press and quickly release the volume button nearest to the top button.
- Press and quickly release the volume button farthest from the top button.
- Press and hold the top button.
- When the Apple logo appears, release the top button.
Force restart iPad (models with the Home button)
Press and hold the top button and the Home button at the same time. When the Apple logo appears, release both buttons.
Next, disconnect and reconnect the USB hub.
If the hub’s Ethernet port was working prior to the iPadOS 16.4, if the problem persists, you may have encountered a bug or unexpected change of functionality. Others have noted issues with some USB connected monitors after updating to iPadOS 16.4 - and as such, it is perhaps not an unreasonable supposition that a hub-connected Ethernet Adapter may also be affected by a new bug.
Should you be unable to resolve the problem, you might be best advised to seek assistance directly from Apple Support. You can contact the Support Team using the Support link at top-right or bottom-left of this page. Alternatively and perhaps easier, you can initiate and manage your support cases using the excellent Apple Support App. If not already installed on your iPad, the App can be downloaded from the App Store:
https://apps.apple.com/app/apple-support/id1130498044
If you suspect a bug, you can submit a Bug Report via Apple’s Product Feedback portal. For iPad and iPadOS:
Feedback - iPad - Apple