We figured this out.
Apple have changed something on their DNS network settings on iOS16.
We were bypassing 8.8.8.8 on our hotspot walled garden script (mainly used for for testing i.e. ping 8.8.8.8 )
I could not reach our local hotspot IP (router gateway IP) or DNS name via phone browser with iOS 16
Removing the walled garden entry for 8.8.8.8 fixed the issue.
Some others having similar issues with other applications here: