iOS 14 & 802.1x authentication

I'm banging my head against the wall on this issue, and I'm afraid it'll only become worse as more devices update to any version of iOS/iPadOS 14. We have an 802.1x network for staff, which is working just fine for MacBooks, Windows devices, and most iPads, but users running iOS/iPadOS 14 are no longer able to connect to the staff network.

Typically, a user will enter their AD credentials, trust a certificate from our domain controller, and be on their way. Now, you just get a 'Unable to join the network "XX-Staff"'. The issue doesn't seem to be server-side, as there aren't even any logs for the user being denied or failing to authenticate.

We have one DC handing out a cert with a 1024-bit RSA key, which works just fine on iOS 12 & 13, but we cannot get any device on 14.0.1, 14.1, or 14.2 to accept the cert. We just get the error that XX-Staff cannot be joined.

We even set up another test network with the same authentication settings, which is using a cert from another domain controller with a 2048-bit RSA key, and we can't get that to work on 14.

I also know that the new private address option isn't an issue; whether that is on or off makes no difference.

Is there something I'm missing?