It sounded like they were encouraging dnsmasq for home use. I migrated to that successfully. My DHCPv6 is working flawlessly now whereas I was never able to get it running smoothly/persistently on ISC.
I understand Kea has more features so I'm a little curious what I'm missing.
I, too, was under the impression that Kea is now mostly out and they're going the dnsmasq route. There were open issues about some basic features with Kea, too: https://github.com/opnsense/core/issues/7475