@epuertat : I cannot see any x509 error in the Prometheus/alert manager/or manager log using a fresh installation of cephadm. If the user does not provide certificates, Cephadm generates self-signed ones by itself and configure the dashboard with these certificates.
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 (Moderate: Red Hat Ceph Storage 4.3 Security and Bug Fix update), 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/RHSA-2022:1716