In pve7, this is the script I was able to use to reinstall ceph without issue:
systemctl restart pvestatd
rm -rf /etc/systemd/system/ceph*
killall -9 ceph-mon ceph-mgr ceph-mds
rm -rf /etc/ceph /etc/pve/ceph.conf /etc/pve/priv/ceph* /var/lib/ceph
pveceph purge
systemctl restart pvestatd
apt...