We are having issue as well with 802.1x and iOS 16+. Works perfectly on iOS 15. If we connect without using the MDM, so supplying a username and password, it will connect. As soon as we manage the device with an MDM, the issue starts, but on some device, after a few "trust certificate", no where, we receive an iOS message saysing this wifi needs to authorize a certificate (not asking for trust but to accept).
Certificate is supplied by the Radius server, which is an internal certificate (we are our own CA).
What’s new for enterprise in iOS 16 - Apple Support
This must be related to this I guess:
Device Management
Managed Device Attestation uses the Secure Enclave and cryptographic attestations to secure communications by managed devices when connecting to services such as MDM, VPN, and 802.1X.
My guess would be that we need to add the trust root / sub CA to the MDM for that particular certificate, but for now, we have tickets opened with MDM and Apple. I do think there is multiple issue with Enterprise Wifi on iOS16...