We currently list: pagerduty, webhook email and slack - Ms Teams was added at 4.15 with the introduction of alertmanager version 0.26 

https://docs.openshift.com/container-platform/4.15/post_installation_configuration/configuring-alert-notifications.html#sending-notifications-to-external-systems_configuring-alert-notifications 

https://github.com/prometheus-operator/prometheus-operator/blob/main/Documentation/api.md#monitoring.coreos.com/v1alpha1.MSTeamsConfig 

AlertmanagerConfig reference:

https://docs.openshift.com/container-platform/4.15/rest_api/monitoring_apis/alertmanagerconfig-monitoring-coreos-com-v1beta1.html#spec-receivers-2