Not gonna lie, getting this to work was hard, plus I'm still not
super happy with the results but it's good enough. You can set
a static ip in the Proxmox cloud-init disk and that's what you'll
end up with on first boot.
Note: this probably also applies to Ubuntu 18.04
At work I upgraded to Ubuntu 16.04 LTS and every time I ran gvim I got a bunch of errors.
(gvim:19805): Gtk-WARNING **: /usr/lib/x86_64-linux-gnu/gtk-2.0/2.10.0/immodules/im-fcitx.so: cannot open shared object file: No such file or directory
(gvim:19805): Gtk-WARNING **: Loading IM context type 'fcitx' failed