This is part of the PR to merge dashboard-ansible and ceph-ansible: https://github.com/ceph/ceph-ansible/pull/3426
With ceph version 14.2.4-85.el8cp ,Ceph-ansible deploys the alertmanager as per the comment in the description. Moving this BZ to verified.
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://access.redhat.com/errata/RHBA-2020:0312