iphones not working with Open DNS

This is a query with what I believe is a fix as well. Recently, I think when the latest IOS version, 14, came out, all the iphones in my home (there are four of them) stopped working en masse with the wifi. This affected safari and all other internet based activity. Only one continued to work, which is still on ios 12. The newer iphones (iphone 8 plus, 8, and new iphone SE) would appear to be connected, but showed up a message saying "this device is not connected to the internet". they all worked fine with the data connection over the telephone network, but not with wifi.

Now I did a lot of troubleshooting, all the usual stuff, turning phones off and on, turning the router off and on, resetting, factory resetting, giving each phonte a manual IP address matched with the router, getting the phones to forget the wifi, resetting the phones network settings. Each time I thought I had found a solution, but without success. Again the phones were fine on data over the phone network but not through our wifi. They were also fine over alternative wifi connections, such as tethering off another phone.

Eventually I tried removing the DNS setting from the router - which is installed as a parental control so that none of the devices can access problematic websites: the DNS servers that block adult content, called OpenDNS FamilyShield: 208.67.222.123 and 208.67.220.123. And that worked.

I've now installed a different DNS on the router, by Cleanbrowsing: 185.228.168.10. And that seems to be working now, at least for the moment. So all good for the moment, but I'm wondering if others have had this problem, and if it's down to this change: "Apple announced the release of iOS 14

on Sept 16, 2020. Among other changes, iOS 14 and macOS 11 include

support for encrypted DNS, and the ability for domain owners to

designate a DNS resolver of their choosing." https://support.opendns.com/hc/en-us/articles/360049861971-DNS-Resolver-Selection-in-iOS-14-and-macOS-11