It only shows email, http and legacy notification. I checked below:
:/usr/share/graylog-server/plugin$ ls -al
total 121692
drwxr-xr-x 2 root root 4096 Jul 5 09:26 .
drwxr-xr-x 4 root root 4096 Jul 5 09:25 ..
-rw-r--r-- 1 root root 22858574 Jun 15 13:36 graylog-plugin-aws-4.2.10.jar
-rw-r--r-- 1 root root 7075812 Jun 15 13:36 graylog-plugin-collector-4.2.10.jar
-rw-r--r-- 1 root root 32919438 Jun 15 13:37 graylog-plugin-integrations-4.2.10.jar
-rw-r--r-- 1 root root 8616855 Jun 15 13:36 graylog-plugin-threatintel-4.2.10.jar
-rw-r--r-- 1 root root 23280631 Jun 15 13:36 graylog-storage-elasticsearch6-4.2.10.jar
-rw-r--r-- 1 root root 29844354 Jun 15 13:36 graylog-storage-elasticsearch7-4.2.10.jar
$ tail -f /var/log/graylog-server/server.log
2022-07-05T09:48:35.783Z INFO [ServiceManagerListener] Services are now stopped.
2022-07-05T09:48:37.230Z INFO [ImmutableFeatureFlagsCollector] Following feature flags are used: {}
2022-07-05T09:48:37.796Z INFO [CmdLineTool] Loaded plugin: AWS plugins 4.2.10 [org.graylog.aws.AWSPlugin]
2022-07-05T09:48:37.797Z INFO [CmdLineTool] Loaded plugin: Integrations 4.2.10 [org.graylog.integrations.IntegrationsPlugin]
2022-07-05T09:48:37.798Z INFO [CmdLineTool] Loaded plugin: Collector 4.2.10 [org.graylog.plugins.collector.CollectorPlugin]
2022-07-05T09:48:37.799Z INFO [CmdLineTool] Loaded plugin: Threat Intelligence Plugin 4.2.10 [org.graylog.plugins.threatintel.ThreatIntelPlugin]
2022-07-05T09:48:37.799Z INFO [CmdLineTool] Loaded plugin: Elasticsearch 6 Support 4.2.10+37fbc90 [org.graylog.storage.elasticsearch6.Elasticsearch6Plugin]
2022-07-05T09:48:37.799Z INFO [CmdLineTool] Loaded plugin: Elasticsearch 7 Support 4.2.10+37fbc90 [org.graylog.storage.elasticsearch7.Elasticsearch7Plugin]