Do you mean hostapd? I'm not aware of any builtin kernel/modules doing AP stuff.
Right, hostapd. It has the radius functionality builtin you'd need for proper wifi enterprise functionality
Getting hostapd to work is ass in itself.
Yes, but much easier than with a full radius server
FWIW one can front-end OpenLDAP or AD with Radius. Once the translation layer is in place then it's more about teaching IT how to manage particular fields in LDAP/AD.