Keycloak has a separate adapter for Jetty 8.1.x that you will have to install into your Jetty installation. You then have to provide some extra configuration in each WAR you deploy to Jetty. Let's go over these steps.

There is a adapter zip file for Jetty 8.1.x in the adapters/ directory in the Keycloak appliance or war distribution. You must unzip this file into Jetty 8.1.x's root directory. Including adapter's jars within your WEB-INF/lib directory will not work! $ cd $JETTY_HOME $ unzip keycloak-jetty81-adapter-dist.zip Next, you will have to enable the keycloak option. Edit start.ini and add keycloak to the options

Enabling Keycloak for your WARs is the same as the Jetty 9.x adapter. Our 8.1.x adapter supports both keycloak.json and the jboss-web.xml advanced configuration. See Required Per WAR Configuration