I recently installed Arch Linux on a fairly old (but not ancient) Intel T2 Mac, with the GNOME DE, and it uses less than 1.5GB of RAM. I went for the standard gnome package which as far as I can tell is "batteries included."

That leaves about 6.5GB for programs, which I think is acceptable.

Less than that, between 900MB and 1.2GB and that's due to file and stuff indexation. The good thing on Linux and BSDs is you can swap for a light wm/compositor and your back below 150MB idle.

> Modern Gnome and KDE distros with batteries included also idea at around 2GB RAM

Really? I'm seeing 1.3 for Mint/Cinnamon.