I spoke to tbrisker on the IRC channel who helped me find the issue. We looked at a couple things and he suggested that it was likely to be an Apache config issue. He was correct; on Debian-based distributions Apache is installed to /etc/apache2, while on RedHat-based distributions it is installed to /etc/httpd. The foreman-installer package accounts for this and installs Apache to the correct folder. However, the keycloak-httpd-client-installer does not account for this difference and just installs to /etc/httpd, so moving the config files from /etc/httpd/conf.d/ over to /etc/apache2/conf.d/ it now takes the user to /users/extlogin with the prompt to sign in via Keycloak.
