Error on attempting to remove IPv6 from LAN interface:
The following input errors were detected:
The DHCPv6 Server is active on this interface and it can be used only with a static IPv6 configuration. Please disable the DHCPv6 Server service on this interface first, then change the interface configuration.
But it's not active.
I have disabled IPv6 completely. I use KEA for IPv4, no IPv6 on the WAN interface at all, and "ISC DHCPv6" shows a lan interface with "Enable DHCPv6 server on LAN interface" not selected.
Kea DHCPv6 is disabled.
I have rebooted multiple times.
Try to disable all "track interface" settings referencing it first.