Following the instructions on https://pve.proxmox.com/wiki/Install_Proxmox_VE_on_Debian_Buster.

First we've pretty extensively cleaned up the installed packages on uffizi (zfs, vlan, etc. needed to go before we could install proxmox). Then we've followed the instructions on the PVE install page.

To add the machine to the proxmox cluster, we followed the GUI instructions of https://pve.proxmox.com/wiki/Cluster_Manager#pvecm_join_node_to_cluster.

This failed (somewhat), as corosync didn't update with the full list of nodes in the cluster (apparently?). Restarting corosync on all nodes made everything come back properly, and uffizi was successfully added to the cluster.

We updated the network config to add a vmbr0 bridge on vlan440. After a reboot, the server came up cleanly.

Afterwards, I cleaned up more packages using aptitude's "local or obsolete packages" feature.
I've also cleaned up the old node definition in puppet (for uffizi.softwareheritage.org), as proxmox needed a reset of the host fqdn (to uffizi.internal.softwareheritage.org). This made icinga2 come back up properly.

The interface on VLAN1330 and VLAN440 were already configured

I used the same template as them to add the interfaces for VLAN442 and VLAN443:

## VLAN443
auto vlan443
iface vlan443 inet manual
	vlan-raw-device bond0

auto vmbr443
iface vmbr443 inet manual
        bridge_ports vlan443

## VLAN442
auto vlan442
iface vlan442 inet manual
	vlan-raw-device bond0

auto vmbr442
iface vmbr442 inet manual
        bridge_ports vlan442

All the networks can now be pinged from a well configured vm.

The server can now be used for experiments