Comment 2 for bug 2010561

Maybe something like this pseudo-code in network-manager preinst maintainer script:

foreach UUID in $(cat /etc/NetworkManager/system-connections/* | grep "^uuid=")
  ORIG_ID=$(nmcli --get-values connection.id con show $UUID)
  nmcli con mod $UUID con-name $ORIG_ID".NETPLAN"
  nmcli con reload
  nmcli con mod $UUID con-name $ORIG_ID

While on it, we should probably also make the network-manager package install a /etc/NetworkManager/system-connections/README file after migration, which states that the existing connection profiles have been migrated to /etc/netplan (and where a backup can be found).