I installed Ubuntu 20.04 from ISO and got screen sharing (viewing on a Mac) working, but I was disappointed with the laggy performance. So I want to try xfce. I installed xfce, and when I restart I can choose Ubuntu, Ubuntu on Wayland, Xfce session, or Xubuntu session. In either of the last two, I see no way to enable/start screen sharing, and the Mac has no Networks choice in the Finder sidebar, and attempting to "Connect to server" to vnc://[system name] gets an error. If I log in to Ubuntu, I can still screen share to the Mac.
The only thing I've found so far is https://softsolder.com/2011/12/18/enabling-remote-desktop-sharing-in-xubuntu/ where someone says you start by "firing up vino-preferences in a terminal" without any details on prerequisites. (Simply typing "vino-preferences" gets a command not found error.)
So... how to get xfce to screen-share?