Apple has introduced private WiFi in the upcoming IOS 14. This is a form of periodic MAC address randomization, and is enabled by default. Here is some more info: https://wifinowglobal.com/news-and-blog/new-private-wi-fi-address-iphone-feature-could-severely-impact-the-wi-fi-industry-expert-says/
I am using unbound with DHCP registration. This seems to at least cause a lot of logspam:
2020-09-01T06:39:57 unbound[4276] dhcpd entry changed DJH.ddns.net @ 192.168.0.128.
2020-09-01T06:39:56 unbound[4276] dhcpd entry changed DJH.ddns.net @ 192.168.0.103.
2020-09-01T06:17:10 unbound[4276] dhcpd entry changed DJH.ddns.net @ 192.168.0.128.
2020-09-01T06:17:10 unbound[4276] dhcpd entry changed DJH.ddns.net @ 192.168.0.103.
2020-09-01T05:47:51 unbound[4276] dhcpd entry changed DJH.ddns.net @ 192.168.0.128.
2020-09-01T05:47:51 unbound[4276] dhcpd entry changed DJH.ddns.net @ 192.168.0.103.
2020-09-01T05:17:09 unbound[4276] dhcpd entry changed DJH.ddns.net @ 192.168.0.128.
Perhaps this is caused by automatic switching between 2.4 and 5 GHz, I'm not sure.
Also I'm not sure about the other implications, perhaps we need to rethink some best practices. For example, I'm using DHCP static mappings to provide devices with fixed IP addresses, but this doesn't seem to be a good idea anymore as it is MAC-address-based.