Just enter journalctl -b -u corosync -u pve-cluster and have this result:
root@pve6:/etc/pve# journalctl -b -u corosync -u pve-cluster
-- Journal begins at Mon 2022-01-10 01:06:40 MST, ends at Mon 2022-01-10 11:27:15 MST. --
Jan 10 05:59:09 pve6 systemd[1]: Starting The Proxmox VE cluster...