hmm, I guess this was the golden hint:
root@CALLISTO:~# cat /etc/pve/.members
{
"nodename": "CALLISTO",
"version": 6,
"cluster": { "name": "JUPITER", "version": 3, "nodes": 2, "quorate": 1 },
"nodelist": {
"CALLISTO": { "id": 2, "online": 1, "ip": "192.168.2.3"},
"GANYMED": { "id": 1...