There was some discussion here: https://pagure.io/SSSD/sssd/issue/2015
Conclusion seems to be that it's hard to automate because a mixed network (IPv4 and
IPv6) doesn't give any good way to automatically choose between the different options.
Another way to approach might be to use /etc/sssd/sssd.conf
At the moment, ipa-client-install ignores/removes any existing /etc/sssd/sssd.conf.
If there was an option to keep an existing sssd.conf (or that were simply the default),
then installer could add ipv6_only or ipv6_first themselves.
It would also allow for setting other options, so long as those options aren't
anything that ipa-client-install wants to override (or maybe even then?).