Is SSSD supported on AIX and Solaris? If so, any good setup guide?
SSSD is not included with either Solaris or AIX. It will not be supported by either vendor (Oracle or IBM) since they do not deliver it as part of the respective OS.
SSSD is a Linux daemon. Solaris and AIX have their own way of handling authentication.
SSSD definitely does not work on AIX. It may work for PAM authentication, since AIX appears to use PAM as the base for its authentication, but AIX does not use NSS, so none of the user/service lookup will work.
It should work on Solaris - Solaris uses both PAM and NSS, and modules for one tend to cross over to the other; however, there could be something Linux-specific in SSSD that doesn't work on the Solaris version of PAM or NSS. Hard to say.