The `keycloak` package prior to version 17.0.1-2 was running with WildFly server. Since upstream officially moved to [Quarkus distribution](https://www.keycloak.org/2020/12/first-keycloak-x-release.adoc), Arch Linux follows this approach. This means some manual intervention is required for the upgrade.
The configuration needs to be adjusted from the old `.xml` format to the new `/etc/keycloak/keycloak.conf`.
Prior to the upgrade, stop the keycloak service, upgrade the package and migrate the configuration before starting:
systemctl stop keycloak.service pacman -Syu keycloak # migrate configuration /etc/keycloak/keycloak.conf systemctl start keycloak.service
See Keycloak [migration docs](https://www.keycloak.org/migration/migrating-to-quarkus) and Keycloak Quarkus [server docs](https://www.keycloak.org/server/configuration)